To get maximum exposure, you should post your question in a new thread, including all of your details such as camera model, cable connections used, operating system used, iMovie version used. Otherwise responses can get confusing since every setup is different.
Most tape based cameras are supported by iMovie, even if not shown on the supported camera list.
However, as I said earlier, importing digital tape can be somewhat hit or miss. There recently have been reported problems with importing DV when running the current Monterey operating system.
Recognition problems can be caused by cable connection issues as well. A faulty cable or faulty or cheap adapter, or a defective computer socket, or a loose connection can cause the Mac not to recognize the camera. Other than loose cables, cable issues may not be visible to the eye, so the only way is to change out the cable and/or adapters to see if they work. Can be a bit of an expense.
Sometimes getting the tape running can trigger recognition.
You might try resetting your System Management Controller (although not available for the new M1 computers). It is easy to do, mostly a matter of booting up while holding down certain keys. This link gives instructions:
How to reset the SMC of your Mac - Apple Support
-- Rich