A friend of mine recently came to me with this problem: His Epson projector was only showing the menu bar from his MacOS desktop. It took us a bit to figure out exactly what his problem was, but in the end, we had to enable “Screen Recording” under Preferences > Security & Privacy > Privacy > Screen Recording.
Now, there could be any number of reasons why your projector might not be working, but I’m posting the above solution for my future reference. If it helps you too, leave a comment letting me know. Otherwise, this post isn’t here to help you troubleshoot other issues and solutions.
Reference: After 45 minutes of troubleshooting, I came upon this forum thread.