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.

To verify if the required API is missing or absent on your Microsoft Tenant, following the 5 minute procedure detailed at:

Verify missing SfB API on Microsoft Tenant

  • If the API is confirmed as absent in the tenant then the issue should be escalated to Microsoft for resolution.

  • If the API is found then refer the issue to Call2Teams support.

If the API is absent then this a solely an issue with Microsoft 365 and has no relation to Call2Teams. We request you report this to us and to Microsoft as detailed below, however the Call2Teams support desk are unable to effect any change that will enable the API in the Microsoft tenant.

Escalating to Microsoft

If this problem will not resolve by waiting or using the first method, then the issue can be escalated to Microsoft. 

  • To do this, log in to the Microsoft 365 admin portal at 
  • Go to the Admin icon
  • On the left hand side menu bar select "Show All" and the Support option will show,
  • Create a support request  
  • Click past any article recommendations in the help center, they won't apply here.

Provide this information:


Teams and Skype for Business Administration API GUID 39624784-6cbe-4a60-afbe-9f46d10fdb27 is missing from my Tenant


This existing open Microsoft ticket #21789731  has this problem symptom under investigation, please report this tenant ID to the product team against this reference.

Following the process detailed at 

My Microsoft 365 tenant reports that the API for Teams and Skype for Business Administration API (GUID 39624784-6cbe-4a60-afbe-9f46d10fdb27) is Not Found

This should contain sufficient information for Microsoft to investigate and address the problem. You will be able to reproduce this error by running through the described process at any time.