Hi Pauline,
When the screen is black, the Viewer in Window 11 says Connecting to XXX. Please wait. (XXX being the name of the Mac). Oddly enough, in Android the screen shows as black, and if I move the mouse, the Mac mouse pointer appears and moves. Linux (Zorin 18) shows a spinning circle!
If I connect to the Mac using Chrome Remote Desktop, the monitor wakes up and becomes viewable on all three operating system devices.
Hope that helps.