M365 Copilot Chat (work) not working in Teams

1. Confirmation of licenses and subscriptions
 Check if your organization has purchased Copilot
Administrators need to check if a Microsoft 365 Copilot subscription exists in the Microsoft 365 Admin Center under Billing > Your Products.
 Assigning licenses to users
The administrator goes to Users > Active Users, selects the target user, and ensures that a Copilot license has been assigned.
2. Update or fix the Teams client
 Update Teams to the latest version
Desktop: Click “...” > “Check for updates” in the upper right corner.
Web: Using Edge/Chrome, press Ctrl+Shift+Delete to clear cache and retry.
Mobile: Go to the App Store and update the Teams app.
 Logging back in or fixing Teams
Log out of Teams and log back in.
Windows users:
Open Settings > Applications > Microsoft Teams > Repair.
If this does not work, select “Uninstall” and reinstall. 
3. Check policy restrictions (requires administrator action)
Verify Teams application permission policies
An administrator accesses the Teams Management Center:
Navigate to Teams Application > Permission Policies and ensure that Copilot is not disabled.
Check that the Messaging Policy allows AI functionality.
Review Compliance Policies
Check if Copilot is restricted due to Data Leakage Prevention (DLP) or compliance policies, and adjust the policies if necessary. 
4. Additional troubleshooting steps
Switch client or network environments
Try switching from the desktop version of Teams to the web version (teams.microsoft.com).
Change networks (e.g., use a cellular hotspot) to troubleshoot corporate network restrictions.
5. Contact Microsoft Support
If the above does not work, administrators can submit a support request through the Microsoft 365 Admin Center.