No, I can’t list the group information for the group id in question. I will contact the server admins and ask for the admin.groups permission for a test run. The ticket creation endpoint mentions ticket.agent permission only, but I will test and come back.
I mean, that the user for them you have the api key needs at least read rights on the given group. You have to set up those rights on the user (agent) config. I think, that you don’t need admin rights.
Sorry for wasting your time, my bad. I just found that a setting in Postman caused the problem. I sent the request body as raw, but let the type setting on text. Changing the type to JSON fixed the problem.