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MediumService Outage · 3 min read

Microsoft Teams Desktop Client Faces Launch Delays for Some Windows Users

Microsoft is investigating a newly acknowledged issue affecting the Microsoft Teams desktop client on Windows. Some users may be unable to launch Teams initially, while others experience loading delays of up to two minutes. Microsoft is tracking the incident as TM1466820 and is currently analyzing service logs and telemetry to determine the underlying cause. As a temporary workaround, Microsoft recommends affected users access Teams through the web client or mobile application while remediation efforts continue.

Written by ThreatBeaconX Research Team·Published Sep 4, 2026

Description

Microsoft has confirmed a known service issue that is preventing some Windows users from opening the Teams desktop application normally. The problem occurs when Teams is initially launched, with affected users either seeing the application fail to load or experiencing a delay of up to approximately two minutes.

The incident was acknowledged under TM1466820, and Microsoft is continuing its investigation.

Technical Description

The issue appears to affect the Teams desktop client running on Windows systems. Microsoft has not yet disclosed a definitive root cause or confirmed whether the problem is related to a software deployment, backend service, client component, or another infrastructure dependency.

Microsoft is reviewing service telemetry and logs and has contacted selected affected users to gather additional information.

Attack Overview

This incident is currently classified as a Microsoft service availability issue, rather than a confirmed cybersecurity attack.

There is no indication in the available information that attackers are exploiting the Teams launch problem or that customer data has been compromised.

Technical Analysis

The reported behavior includes:

  • Teams desktop client failing to load during initial startup.
  • Launch delays of up to approximately two minutes for some Windows users.
  • Microsoft tracking the incident as TM1466820.
  • Microsoft analyzing telemetry and service logs to isolate the underlying cause.
  • No confirmed security vulnerability or exploitation associated with this incident at the time of reporting.

Microsoft is also investigating a separate issue affecting Teams for Mac, where some users are unable to join calls or meetings. That incident is tracked separately as TM1466659.

IOC

No IOCs identified or reported.

Potential Impact

Organizations experiencing the issue may face:

  • Delayed access to Teams.
  • Temporary inability to use the desktop client.
  • Disruption to collaboration and communication.
  • Increased dependency on alternative Teams access methods.
  • Potential productivity impact for users relying exclusively on the desktop application.

Recommendations

Immediate Actions

  • Use Microsoft Teams on the web if the desktop client fails to load.
  • Use the Teams mobile application as an alternative access method.
  • Monitor Microsoft 365 service-health communications for updates.
  • Avoid repeatedly reinstalling Teams unless Microsoft specifically recommends it.
  • Document affected endpoints and users for internal troubleshooting.

Preventive Actions

  • Maintain alternative communication channels for critical business operations.
  • Ensure users can access Teams through supported web and mobile platforms.
  • Monitor Microsoft 365 service-health events.
  • Maintain an updated inventory of Teams client versions and supported Windows platforms.
  • Include SaaS collaboration-platform outages in business continuity planning.

Conclusion

The Teams desktop-client problem is currently being investigated by Microsoft and appears to be a service availability issue rather than a confirmed security incident. Organizations affected by the disruption can temporarily use Teams through the web or mobile application while Microsoft works to identify the root cause and implement remediation.