I had the same issue with the following but i did not manage to resolve it.
I found two “assume identity” permissions. 1.Assume Agent Identity , 2. Assume Requester Identity under the new admin role i created.
I checked them both, but the problem persists.
Any idea what should i do to fix the issue?
Thanks in advance!
Related topic: Getting a Permissions Error when Importing Notes/Replies for any agents