Error: Could not add group ... to release ...

[OliverLippertVw]

For others, Google and probably my "future me":

If you create an group of testers on the organization level, you can see the following error, if you create the wrong kind of token

Error: Could not add group ... to release ...

Instead of creating an App API tokens (appcenter.ms > open application > open settings > App API tokens) you need to create an User API token.

To be honest: There is a slight hint in the token parmeter description already, but for security reasons I decided to create an App API token. For one workflow it worked but in some other workflow we distribute to some other project in MS App Center and there the very same step (matrix job) failed.