FaceTime: no video, audio ok, camera ok

Let me preface by indicating that the problem is only on my iMac (Monterey) and not on my other devices (iPhone, iPad).

FaceTime: opening the app, I see an image of myself thus the camera is not the problem.

Making or receiving a video call, I briefly see the other person's image which then disappears and m left with a grey screen with a triangle in the middle.

The caller CAN see and hear me and but can only hear them.

I'm truly stumped what can be nixing the video feed seeing that the camera is fine, my internet connection is good (my other devices have no problem) and the iMac is connected by Ethernet and wifi.

Any thoughts? Thanks