In NINA, did you go to Options > General and turn on Enable Server? This turns on the API service that APPM must use to access the camera via NINA.
I had the same "problem" and have found that in recent NINA 1.11 updates, that specific setting isn't stored in the profile anymore or at least seem to be reset to default (=disabled) with each re-install even without uninstallling NINA
first.
I don't recall having to do so with every update when I first started using NINA last summer. I suppose there's a reason for that but
haven't inquire about it on the NINA discord.
