Strange, I am using essentially this exact set up (11.2, Monterey, AH mk1) and it works totally fine for me. Use it for mastering purposes like this all the time.
Do you have the latest firmware installed on the Heat?
I have the same issue with the latest overbridge Analog Heat VST3 plugin in ableton on PC.
When I load the VST2 plugin it will work on the audio track as an effect, however the VST3 only loads in an instrument track? Workaround for me is to use the VST 2 version.
I’ve got the same problem. The VST3 is listed in Cubase plugin manager as an instrument rather than an effect, so it can’t be selected as an effect on any of the tracks. In the ‘category’ field in plugin manager it says ‘Instrument|Effect’ - I think Elektron need to change this for it to work, because I can’t see any way to edit it as a user