screen sharing

I tried to share my desktop during a small meeting today and a white window popped up. Nothing else. I have a iMac laptop and the OS is up to date. I deleted the Zoom desktop app and reinstalled. My meeting host shared the meeting link again, and I still got the while blank window. Others in the meeting are able to share their desktops. Mac support assisted in checking privacy setting and they ado not block sharing screen. Does anyone know why this is happening and how to fix this problem? I am on a basic free plan.