Outage in Microsoft 365
SIP devices can't make or receive calls
Resolved Minor
October 21, 2026 - Started 6 days ago
- Lasted about 21 hours
Incident Report
Summary AI Generated
A configuration issue affecting components that manage SIP devices caused users to be unable to make or receive calls, with devices disconnecting upon synchronization and users unable to sign back in. The issue lasted approximately 20.7 hours and impacted any SIP device user, while Teams web, desktop clients, and Teams Phone Devices remained unaffected. Microsoft deployed a fix to the affected infrastructure, confirmed service restoration with multiple organizations, and continued monitoring to validate full recovery.
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
Components affected
Microsoft TeamsTrusted by 1,000+ teams
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Latest Updates ( sorted recent to last )
5 days ago - at 10/22/2026 04:00PM
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
5 days ago - at 10/22/2026 11:50AM
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
5 days ago - at 10/22/2026 07:50AM
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
6 days ago - at 10/22/2026 02:58AM
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
6 days ago - at 10/21/2026 10:52PM
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
6 days ago - at 10/21/2026 08:20PM
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
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