Are there any problems starting Microsoft Teams?

Yes. Microsoft documents several known causes when Teams appears to start but does not open, opens a blank window and closes, or fails when switching to new Teams.

Common causes include:

1. Network access issues
   • Teams can fail to launch if firewall or proxy settings block access to Teams endpoints.
2. User profile or AppData folder issues
   • The new Teams app may not start if:
     • Cookies or Cache shell folders point to a reparse point.
     • TEMP or TMP point to a reparse point.
     • Required folders under AppData are missing permissions.
     • Some AppData folders are reparse points.
     • Invalid files exist with the same names as required system folders.
     • SYSTEM or Administrators lack Full control on required folders.
     • The Teams install location is missing SYSAPPID permission.
3. Windows policy or OS version issues
   • The AllowAllTrustedApps policy can prevent new Teams from starting.
   • Unsupported or older Windows builds can also block launch.
4. Third-party software conflicts
   • Dell Encryption is known to corrupt Teams during updates and can cause a permanent failure to start.

Useful checks and fixes:

1. If using new Teams, check whether the issue matches the known launch problem:
   • In classic Teams, if turning on Try the new Teams shows Something went wrong, this is a known scenario.
2. Check network configuration
   • Verify that firewall or proxy settings are not blocking Teams endpoints.
3. Check for Dell Encryption
   • If Dell Encryption is installed, exclude:
     • %LocalAppData%\Microsoft\Teams
   • This avoids corruption during Teams updates.
4. Check Windows version and policy
   • Run winver.
   • If Windows is older than these builds, the AllowAllTrustedApps setting may need to be enabled:
     • Windows 11 21H2 build 22000.2777
     • Windows 11 22H2 build 22621.2506
     • Windows 10 21H2 build 19044.4046
     • Windows 10 22H2 build 19045.3636
   • If needed, check AllowAllTrustedApps in:
     • Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock
     • Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Appx
   • If the value is 0, change it to 1.
   • Warning: Registry changes can cause serious problems if done incorrectly. Back up the registry first.
5. Check AppData-related conditions
   • Verify that Cookies, Cache, TEMP, and TMP do not point to reparse points.
   • Verify Read access to required AppData folders.
   • Verify required folders are not replaced by files of the same name.
   • Verify SYSTEM and Administrators have Full control where required.
6. If the issue persists
   • If AppData folders were changed to reparse points, contact Microsoft Support.
   • If the system is on an older build, update to Windows 11 version 22H2 build 22621.2506 or later.

• Dell Encryption prevents Teams from starting correctly
• Resolve issues when starting the new Teams app
• Resolve Teams client launch failures