Applies To


If in the pop-up "Acquiring Microsoft Access Token - invalid_client " is seen, then this indicates that the Microsoft Office 365 tenant is not fully setup, or the setup has failed.

Reason 1: Office 365 internal setup has failed

On rare occasions the Microsoft Office 365 system orchestration can fail and provision services out of sequence. This leads to a lock-state on some of the elements within the Office 365 permissions database. This situation has occurred when Teams is under heavy load due to extraordinary circumstances.


The Azure permissions for Call2Teams (or relevant brand application) have to be removed and the setup run again.

  • Browse to   
  • Select "All Services"  
  • Click on "Azure Active Directory"     
  • In the Manage section on the left menu bar, Click on "Enterprise Applications"     
  • Click on the branded Call2Teams application to open a new screen    
  • Click on "Properties"    
  • Click "Delete" and confirm     
  • Wait 1 minute     
  • Access Call2Teams again and give consent

Reason 2: The API needed for authentication is missing from the Microsoft 365 tenant

A standard Microsoft API is required for the automatic setup process to properly function. On some Microsoft tenants this API is absent and the process fails.

Install the API to the Microsoft tenant by following this process:

Azure Maintenance in PowerShell to Install Missing API