My Apple desktop monitor isn't recognized as an external monitor with my MacBook Pro
I have a MacBook Pro running Big Sur 11.2.3. I have been using my old Apple desktop as an external monitor (running Catalina version 10.15.7; it won't support Big Sur) for a few months with the last Big Sur update (I think 11.2.2 but not sure). Yesterday, out of the blue, my MacBook Pro quit recognizing my Mack desktop as an external monitor. I just updated Big Sur to 11.2.3 hoping that would fix the problem. It didn't. They are connected with a USB to USB C adapter.
There are alot of similar problems with Big Garbage Sur with external monitors but no questions I found that specifically are for an Apple desktop as an external monitor.
Any solutions? If I can't use my laptop with an external monitor, I might as well throw it out the window and go back to Windows. SO DISAPPOINTED IN APPLE LATELY.
Thanks
MacBook