Problem exiting "share screen"

I was recording a speech on my MacBook Air and showing a PPT. When the speech ended, I could not "stop share." I couldn't get control of my mouse to stop the recording either. Somehow it started a whiteboard and was just drawing little squiggles. Someone with IT exp offered to take remote control but I couldn't control my mouse to accept her offer. After 9 minutes of trying everything I could think of, I finally shut off my computer to stop the Zoom recording and escape--obviously destroying the recording of the speech in the process. Any idea what went wrong here?