Microsoft 365 Alert – Service Degradation – Microsoft Teams – Users with non-ANSI characters in their alias may be unable to launch the Microsoft Teams desktop client – RESOLVED

15/05/2026 02:23:00 PM

NHSmail Reference: INC46827776

Microsoft Reference: TM1311440

Issue Status: RESOLVED

Issue Description: Some users with non-ANSI characters in their alias may be unable to launch the Microsoft Teams desktop client

More info: Affected users may be unable to launch the Microsoft Teams desktop client due to failures during character encoding conversion.

Final Update: 20/05/2026 09:15:00 AM–Microsoft has confirmed that the fix has been deployed to the affected environment and is now available in build 26106.1911.4707.3286. Their system telemetry indicates no further crash events, and impact has been mitigated.

Scope of impact: Impact is specific to some users attempting to launch the Microsoft Teams desktop client.

Root cause: A character encoding issue during Teams client start-up is causing failures for users with certain Unicode characters in their aliases.

Next steps: Microsoft are reviewing Teams client start-up telemetry to ensure stability across affected users and to prevent similar issues in future updates