💡 Our Technical Review in summary
Summary
Microsoft has resolved a service issue where admins were unable to deploy custom add-ins through the Microsoft 365 admin center, and end-users were blocked from accessing existing add-ins. The issue was triggered by a service update intended to enforce stricter authentication requirements, which inadvertently blocked deployment and user authentication requests.
Impact
- Admins: Encountered an error message stating “Learn more about eligibility requirements” when attempting to deploy custom add-ins.
- End-Users: Experienced an inability to access previously deployed add-ins in services such as Exchange Online.
- Affected Add-ins: Specifically validated impact included My Templates, Salesforce, and Viva Insights, though other custom add-ins may have been affected.
- Duration: The issue persisted from January 21, 2026, to March 19, 2026.
Status
Service Restored. Microsoft successfully deployed a code fix to correct the authentication infrastructure mismatch. Service health telemetry and user feedback have confirmed that the impact is fully remediated. Microsoft is currently reviewing testing procedures to prevent similar authentication-related deployment issues in the future.
Microsoft Official Issue Details
User Impact
Admins may have been unable to deploy custom add-ins from the Microsoft 365 admin center.
Status: serviceRestored
Service: Microsoft 365 suite
Classification: advisory
Origin: microsoft
Updates
- 2026-03-20 18:21
Title: Some admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and users can’t access add-insUser impact: Admins may have been unable to deploy custom add-ins from the Microsoft 365 admin center.
More info: Admins may have seen an error that stated, “Learn more about eligibility requirements”
Final status: Our deployment has completed and we’ve confirmed through service health telemetry and with a subset of affected users that the impact is remediated.
Scope of impact: Any admin that attempted deploy custom add-ins from the Microsoft 365 admin center may have been impacted.
Start time: Wednesday, January 21, 2026, at 10:27 AM UTC
End time: Thursday, March 19, 2026, at 7:00 PM UTC
Root cause: A recent service change designed to enforce stricter authentication requirements blocked admins from deploying custom add-ins from the Microsoft 365 admin center.
Next steps:
– We’re reviewing our service change testing and validation procedures to identify and prevent similar issues with authentication requirements in deployments moving forward.This is the final update for the event.
- 2026-03-18 21:33
Title: Some admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and users can’t access add-insUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and users can’t access add-ins.
More info: Admins see an error stating “Learn more about eligibility requirements”
Current status: Our fix deployment has saturated across approximately 50 percent of the impacted environment and is projected to complete and for impact to be remediated by our next scheduled communication update.
Scope of impact: Some admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Start time: Wednesday, January 21, 2026, at 10:27 AM UTC
Root cause: A recent service change designed to enforce stricter authentication requirements blocked admins from deploying custom add-ins from the Microsoft 365 admin center.
Next update by: Friday, March 20, 2026, at 7:00 PM UTC
- 2026-03-18 16:29
Title: Some admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and users can’t access add-insUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and users can’t access add-ins.
More info: Admins see an error stating “Learn more about eligibility requirements”.
Users also report being unable to access deployed add-ins in relevant services such as Exchange Online. Affected add-ins we’ve validated include, but may not be limited to, the following:
– My Templates add-in
– Salesforce add-ins
– Viva Insights add-insCurrent status: Following our completed internal tests with affected users, we’ve confirmed that our fix will be viable for remediating the impact. Our fix has completed approximately 25 percent of the necessary deployment, and since beginning, our internal service telemetry is reporting a reduction of internal add-in errors. As we monitor the remaining deployment, we’ll provide an updated timeline for impact being remediated once it has become available.
Scope of impact: Some admins may be unable deploy custom add-ins from the Microsoft 365 admin center and all users may be unable to access deployed add-ins. This information may be updated as our investigation continues.
Start time: Wednesday, January 21, 2026, at 10:27 AM UTC
Root cause: A recent service change designed to enforce stricter authentication requirements blocked admins from deploying custom add-ins from the Microsoft 365 admin center and blocked user authentication requests from completing.
Next update by: Wednesday, March 18, 2026, at 10:00 PM UTC
- 2026-03-17 21:29
Title: Some admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and users can’t access add-insUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and users can’t access add-ins.
More info: Admins see an error stating “Learn more about eligibility requirements”.
Users also report being unable to access deployed add-ins in relevant services such as Exchange Online. Affected add-ins we’ve validated include, but may not be limited to, the following:
– My Templates add-in
– Salesforce add-ins
– Viva Insights add-insCurrent status: We’ve merged communications discussing impact to deployment or access to custom add-ins into a single communication to provide more streamlined and consistent feedback on our mitigation actions. We’ve updated the “Title”, “User impact”, “Scope of impact”,”Start time”, and “Root cause” fields of this communication to reflect this change. We’ve deployed a code fix designed to correct the offending code mismatch in our authentication infrastructure to a subset of our service infrastructure, and we’re testing for remediation with a subset of affected users prior to initiating a wider deployment. We aim to provide a timeline to wider deployment at the time of our next scheduled update.
Scope of impact: Some admins may be unable deploy custom add-ins from the Microsoft 365 admin center and all users may be unable to access deployed add-ins. This information may be updated as our investigation continues.
Start time: Wednesday, January 21, 2026, at 10:27 AM UTC
Root cause: A recent service change designed to enforce stricter authentication requirements blocked admins from deploying custom add-ins from the Microsoft 365 admin center and blocked user authentication requests from completing.
Next update by: Friday, March 20, 2026, at 8:30 PM UTC
- 2026-03-11 06:14
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: The full deployment of our fix is expected to take an extended period of time, so we’re shifting our efforts to focus on expediting the deployment process. We anticipate that we’ll be able to provide an updated remediation timeline, by our next scheduled update.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Start time: Wednesday, February 25, 2026, at 12:00 PM UTC
Root cause: A recent service change designed to enforce stricter authentication requirements blocked admins from deploying custom add-ins from the Microsoft 365 admin center.
Next update by: Tuesday, March 17, 2026, at 10:30 PM UTC
- 2026-03-10 22:20
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: The deployment of our fix is expected to take an extended period of time, so we’re evaluating possible options to expedite the deployment.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Start time: Wednesday, February 25, 2026, at 12:00 PM UTC
Root cause: A recent service change designed to enforce stricter authentication requirements blocked admins from deploying custom add-ins from the Microsoft 365 admin center.
Next update by: Wednesday, March 11, 2026, at 12:30 AM UTC
- 2026-03-09 21:04
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: We’ve correlated the increase in 401 authentication errors to a recent service change designed to enforce stricter authentication requirements, which blocked admins from deploying custom add-ins from the Microsoft 365 admin center. We’re deploying a fix that’ll unblock the authentication and remediate the impact.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Start time: Wednesday, February 25, 2026, at 12:00 PM UTC
Root cause: A recent service change designed to enforce stricter authentication requirements blocked admins from deploying custom add-ins from the Microsoft 365 admin center.
Next update by: Tuesday, March 10, 2026, at 10:30 PM UTC
- 2026-03-05 22:38
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: We’re continuing our analysis of the increase in 401 errors that may be contributing to impact as a part of our active investigation into the underlying root cause of this event.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Next update by: Monday, March 9, 2026, at 10:30 PM UTC
- 2026-03-04 21:59
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: We’ve identified an increase in 401 errors that may be contributing to impact, and we’re further analyzing the errors to isolate a potential root cause and determine how to best remediate impact.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Next update by: Thursday, March 5, 2026, at 11:30 PM UTC
- 2026-03-04 01:38
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: We’re continuing our analysis of the most recently-collected service logs and data to gain insight into the underlying exceptions contributing to impact and determine our options for remediation.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Next update by: Wednesday, March 4, 2026, at 11:30 PM UTC
- 2026-03-03 21:37
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: While our review of any recent changes made to the service is ongoing, we’re preparing to test some potential mitigative actions with a subset of users to see if they help recover the scenario.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Next update by: Wednesday, March 4, 2026, at 2:30 AM UTC
- 2026-03-03 21:23
Title: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin centerUser impact: Admins may be unable to deploy custom add-ins from the Microsoft 365 admin center and get an error.
More info: Admins may see an error stating “Learn more about eligibility requirements”.
Current status: This is a continuation of EX1243054. We’re reviewing any recent changes made to the service that may have introduced this issue to further our understanding of the underlying cause of the problem and formulate a remediation plan.
Scope of impact: Admins may be unable deploy custom add-ins from the Microsoft 365 admin center. This information may be updated as our investigation continues.
Next update by: Tuesday, March 3, 2026, at 11:00 PM UTC
