SIP devices can't make or receive calls

Title: SIP devices can't make or receive calls User impact: Users may have been unable to make or receive calls using SIP devices. More info: Users may have been unable to sign in to their SIP devices or encountered "Service Unavailable" errors. Once a SIP device attempted to perform its next synchronization, the device would have disconnected. Users would have been unable to log back into those devices and therefore could not make or receive calls using those SIP devices. Calling functionality using the Microsoft Teams web and desktop clients, or Teams Phone Devices was not impacted. Final status: We received additional confirmations from previously impacted organizations that the issue is resolved, and SIP devices are performing as expected. Scope of impact: Any user attempting to make or receive calls using SIP devices were impacted by this event. Start time: Wednesday, October 21, 2026, at 6:00 PM UTC End time: Thursday, October 22, 2026, at 3:30 PM UTC Root cause: A configuration issue had impacted components that manage SIP devices, resulting in impact. Next steps: - We're reviewing the affected systems to identify improvements that could prevent similar issues from recurring. This is the final update for the event.

Title: SIP devices can't make or receive calls User impact: Users may be unable to make or receive calls using SIP devices. More info: Users may be unable to sign in to their SIP devices or encounter "Service Unavailable" errors. Once a SIP device attempts to perform its next synchronization, the device will disconnect. Users will be unable to log back into those devices and therefore can't make or receive calls using those SIP devices. Calling functionality using the Microsoft Teams web and desktop clients, or Teams Phone Devices are not impacted. Current status: We continue to monitor service recovery after the fix completed deployment. We've received confirmation from some organizations that SIP devices are now performing as expected. We're contacting other organizations for further validations. Scope of impact: Any user attempting to make or receive calls using SIP devices are impacted by this event. Root cause: A configuration issue has impacted components that manage SIP devices, resulting in impact. Next update by: Thursday, October 22, 2026, at 8:00 PM UTC

Title: SIP devices can't make or receive calls User impact: Users may be unable to make or receive calls using SIP devices. More info: Users may be unable to sign in to their SIP devices or encounter "Service Unavailable" errors. Once a SIP device attempts to perform its next synchronization, the device will disconnect. Users will be unable to log back into those devices and therefore can't make or receive calls using those SIP devices. Calling functionality using the Microsoft Teams web and desktop clients, or Teams Phone Devices are not impacted. Current status: We've deployed a fix to the affected infrastructure and we've observed a restoration of some of the affected functionality. We're closely monitoring SIP device reconnections and calling stability while conducting additional mitigation actions to push towards a full recovery. Scope of impact: Any user attempting to make or receive calls using SIP devices is impacted by this event. Next update by: Thursday, October 22, 2026, at 4:00 PM UTC

Title: SIP devices can't make or receive calls User impact: Users may be unable to make or receive calls using SIP devices. More info: Users may be unable to sign in to their SIP devices or encounter "Service Unavailable" errors. Once a SIP device attempts to perform its next synchronization, the device will disconnect. Users will be unable to log back into those devices and therefore can't make or receive calls using those SIP devices. Calling functionality using the Microsoft Teams web and desktop clients, or Teams Phone Devices are not impacted. Current status: Our fix is progressing through validation, alongside additional measures to support a safe and stable recovery. Once validation is complete, we'll deploy the fix to the affected infrastructure to begin restoring the affected functionality. Scope of impact: Any user attempting to make or receive calls using SIP devices is impacted by this event. Next update by: Thursday, October 22, 2026, at 12:00 PM UTC

Title: SIP devices can't make or receive calls User impact: Users may be unable to make or receive calls using SIP devices. More info: Users may be unable to sign in to their SIP devices or encounter "Service Unavailable" errors. Once a SIP device attempts to perform its next synchronization, the device will disconnect. Users will be unable to log back into those devices and therefore can't make or receive calls using those SIP devices. Calling functionality using the Microsoft Teams web and desktop clients, or Teams Phone Devices are not impacted. Current status: We're continuing to validate our fix and the recovery of SIP devices within our internal environment. We're also validating additional protective measures before restoring the affected functionality. Once we've confirmed these changes are operating as expected, we'll begin our restoration actions and monitor affected SIP devices as they recover. Scope of impact: Any user attempting to make or receive calls using SIP devices is impacted by this event. Next update by: Thursday, October 22, 2026, at 8:00 AM UTC

Title: SIP devices can't make or receive calls User impact: Users may be unable to make or receive calls using SIP devices. More info: Once a SIP device attempts to perform its next synchronization, the device will disconnect. Users will be unable to log back into those devices and therefore can't make or receive calls using those SIP devices. Calling functionality using the Microsoft Teams web and desktop clients, or Teams Phone Devices are not impacted. Current status: We’re validating a fix within our internal environments and monitoring how SIP devices recover after the fix is applied. This validation is also helping us determine how long affected devices may take to return to normal functionality once the fix is applied. Once validation is complete, we’ll use the results to guide our remediation and restoration actions. Scope of impact: Any user attempting to make or receive calls using SIP devices is impacted by this event. Next update: Thursday, October 22, 2026, at 2:00 AM UTC

Title: SIP devices can't make or receive calls User impact: Users may be unable to make or receive call using SIP devices. More info: Once a SIP device attempts to perform its next synchronization, the device will disconnect. Users will be unable to log back into those devices and therefore can't make or receive calls using those SIP devices. Calling functionality using the Microsoft Teams web and desktop clients, or Teams Phone Devices are not impacted. Current status: We’ve identified the underlying root cause and we are working on developing a fix. Scope of impact: This issue could impact any SIP device. Next update: Wednesday, October 21, 2026 at 11:00 PM UTC