Outage in Microsoft 365
Users may be unable to sign in to OneNote using iOS devices
Resolved Minor
August 14, 2026 - Started about 1 month ago
- Lasted 7 days
Incident Report
Summary AI Generated
A code change in OneNote builds 16.112.717.0 and above, intended to modify authentication request routing, broke the iOS Authenticator broker sign-in flow, preventing affected users from signing into OneNote on iOS devices starting July 20, 2026. The issue persisted for over 174 hours, with workarounds including using OneNote on the web, removing the Authenticator app to fall back to in-app authentication, or signing into another Microsoft 365 app first. A code fix was developed and deployed, though completion took longer than anticipated while monitoring continued.
Title: Users may be unable to sign in to OneNote using iOS devices
User impact: Users may be unable to sign in to OneNote using iOS devices.
Current status: We've identified that a recent change to the sign in flow may be causing impact to occur. We've reverted the change but this did not resolve the issue. We're analyzing OneNote logs from impacted users as well as OneNote logs from our internal reproduction of the issue to assist us in identifying the underlying root cause of impact.
Scope of impact: Any user attempting to sign in to OneNote build 16.112.717.0 or higher using iOS devices is impacted.
Next update by: Friday, August 14, 2026, at 2:00 PM UTC
User impact: Users may be unable to sign in to OneNote using iOS devices.
Current status: We've identified that a recent change to the sign in flow may be causing impact to occur. We've reverted the change but this did not resolve the issue. We're analyzing OneNote logs from impacted users as well as OneNote logs from our internal reproduction of the issue to assist us in identifying the underlying root cause of impact.
Scope of impact: Any user attempting to sign in to OneNote build 16.112.717.0 or higher using iOS devices is impacted.
Next update by: Friday, August 14, 2026, at 2:00 PM UTC
Components affected
Microsoft 365 appsTrusted by 1,000+ teams
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Latest Updates ( sorted recent to last )
about 1 month ago - at 08/18/2026 04:57AM
Title: Users may be unable to sign in to OneNote using iOS devices
User impact: Users may be unable to sign in to OneNote using iOS devices.
More info: Impact is specific to users with OneNote build 16.112.717.0 or higher.
Whilst we work on remediation, impacted users may be able to utilize OneNote on the web or remove Authenticator so that authentication falls back to the in-app webview. Users may also be able to sign in to any other Microsoft 365 apps first (e.g. PowerPoint), then attempt to sign in again in OneNote.
Current status: Our fix deployment is taking longer than anticipated but is ongoing. We're continuing to monitor as it progresses to establish a completion timeline.
Scope of impact: Any user attempting to sign in to OneNote build 16.112.717.0 or higher using iOS devices is impacted.
Start time: Monday, July 20, 2026, at 4:36 AM UTC
Root cause: A code change included in OneNote builds 16.112.717.0 and above, designed to change how authentication requests are routed, introduced an issue with OneNote iOS Authenticator broker sign-in and is causing impact.
Next update by: Friday, August 21, 2026, at 4:00 AM UTC
about 1 month ago - at 08/14/2026 03:55PM
Title: Users may be unable to sign in to OneNote using iOS devices
User impact: Users may be unable to sign in to OneNote using iOS devices.
More info: Impact is specific to users with OneNote build 16.112.717.0 or higher.
Whilst we work on remediation, impacted users may be able to utilize OneNote on the web or remove Authenticator so that authentication falls back to the in-app webview. Users may also be able to sign in to any other Microsoft 365 apps first (e.g. PowerPoint), then attempt to sign in again in OneNote.
Current status: We've identified that a code change included in OneNote builds 16.112.717.0 and above, designed to change how authentication requests are routed, introduced an issue with OneNote iOS Authenticator broker sign-in and is causing impact. We're deploying a code fix to correct this issue and expect that it'll complete deployment by the time of our next update.
Scope of impact: Any user attempting to sign in to OneNote build 16.112.717.0 or higher using iOS devices is impacted.
Start time: Monday, July 20, 2026, at 4:36 AM UTC
Root cause: A code change included in OneNote builds 16.112.717.0 and above, designed to change how authentication requests are routed, introduced an issue with OneNote iOS Authenticator broker sign-in and is causing impact.
Next update by: Tuesday, August 18, 2026, at 6:00 AM UTC
about 1 month ago - at 08/14/2026 01:49PM
Title: Users may be unable to sign in to OneNote using iOS devices
User impact: Users may be unable to sign in to OneNote using iOS devices.
More info: Impact is specific to users with OneNote build 16.112.717.0 or higher.
Whilst we work on remediation, impacted users may be able to utilize OneNote on the web or remove Authenticator so that authentication falls back to the in-app webview. Users may also be able to sign in to any other Microsoft 365 apps first (e.g. PowerPoint), then attempt to sign in again in OneNote.
Current status: We've identified an issue with the OneNote iOS Authenticator broker sign-in and are working on developing and validating a fix to remediate impact.
Scope of impact: Any user attempting to sign in to OneNote build 16.112.717.0 or higher using iOS devices is impacted.
Root cause: An issue with the OneNote iOS Authenticator broker sign-in is preventing users from signing in to OneNote using iOS devices.
Next update by: Friday, August 14, 2026, at 4:00 PM UTC
about 1 month ago - at 08/14/2026 11:53AM
Title: Users may be unable to sign in to OneNote using iOS devices
User impact: Users may be unable to sign in to OneNote using iOS devices.
Current status: We've identified that a recent change to the sign in flow may be causing impact to occur. We've reverted the change but this did not resolve the issue. We're analyzing OneNote logs from impacted users as well as OneNote logs from our internal reproduction of the issue to assist us in identifying the underlying root cause of impact.
Scope of impact: Any user attempting to sign in to OneNote build 16.112.717.0 or higher using iOS devices is impacted.
Next update by: Friday, August 14, 2026, at 2:00 PM UTC
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