Applies To

Call2Teams - Customers


Call2Teams relies on a high-degree of automation to provision the service into Office 365 and to manage the service with the Sync Now feature.

Some customers have encountered an issue with a missing API in their Azure Tenant that leads to a problem provisioning the service, receiving Invalid_Client error on first sync.

The process below outlines the test a customer can perform to verify the presence of the Application Programming Interfaces (APIs) required in their Office 365 tenant. 

Where the API is not found, then Microsoft should be notified as this demonstrates a provisioning issue with the build of the Office 365 tenant that Microsoft need to resolve. However, in most cases it is worth following the PowerShell guidance in this document before doing so, to be sure.

Verification Process

Log in to the Microsoft 365 admin center using credentials with Global Admin privileges


Click Show All on the menu

Open Azure Active Directory

In the Active Directory Admin Center click on Azure Active Directory

In the Overview menu click on App Registrations

Click to create New Registration

Give the App a Name (not important)

Select option for Accounts in any organizational directory (Any Azure AD directory - Multitenant)

Click Register

For your created app select API Permissions

Then select Add a Permission

Request permission for the API by 

Select API my organization uses

The search box needs this GUID to be pasted in: 39624784-6cbe-4a60-afbe-9f46d10fdb27

If you receive the result 'No Results' then the API is absent in your Microsoft tenant

On a good tenant the result below will re returned:

Using PowerShell to Install Missing API

The following actions are required to fix the Microsoft tenant so the service can be deployed:

Install the Azure PowerShell module

Follow the instructions below :
(also available at

On a Windows PC, Run PowerShell as administrator

PowerShell will now launch in Administrator mode

Run the following command: 

Install-Module -Name Az -AllowClobber  

PowerShell will take a few moments to install some dependent modules. Approve these installation requests:

Finally run these two commands to login, and install the API endpoints to the tenant:


New-AzADServicePrincipal -ApplicationId "39624784-6cbe-4a60-afbe-9f46d10fdb27"

If you receive an error you may need to first run   set-executionpolicy remotesigned

The following should be returned from PowerShell and the issue is resolved: