Power BI API with service principal - 401 unauthorized

Hello everyone,

recently I have been trying to make Power BI APIs work with service principal authentication. All steps mentioned in this article https://docs.microsoft.com/en-us/power-bi/developer/embedded/embed-service-principal are done:

- an Azure AD app is registered (service principal created)

- an AD security group is created, the app is added to this group

- a Power BI admin has enabled service principal access in the admin portal

- the service principal and the security group are added to the workspace (and granted the admin role)

I am able to generate an access token using the POST method for https://login.microsoftonline.com/common/oauth2/token (screenshot below).

The issue is that whenever this token is used for any further calls (I have tried both non-admin and admin APIs - when it comes to admin ones, I only tested the supported APIS - can be seen in this article https://docs.microsoft.com/en-us/power-bi/admin/read-only-apis-service-principal-authentication), I am shown the 401 unauthorized error.

So my question is: did I overlook some security setting perhaps? Our company uses MFA, but service principals do not use that from what I have found on this forum/in the documentation. Or is the generated token invalid somehow?

Any help is greatly appreciated.