Interestingly enough, Leeneia, I had *exactly* the same problem around a month ago, and the solution was identical - again, after a lot of to-ing and fro-ing and cross-checking of everything and every permutation, it required uninstall then reinstall. Which then involved re-storing all my settings (a pain!). I since learned that the root cause was very likely the installation of an update around that time which had triggered some kind of bug and the tripping out of the default device recognition. Hence...
Yes, it seems to be impossible to get to actually TALK to Zoom Support - the online chat facility is just "one solution fits all" robot standard (as with so many organisations these days).