Hi ambrose, did you ever see the permission dialog that drops down from the left end of the address bar? This is how it looks on Windows when I tell Google Meet that I want to "Present" (with the default "Always Ask" permission): <center><img src="https://user-media-prod-cdn.itsre-sumo.mozilla.net/uploads/images/2020-05-27-17-23-04-a09897.png" width="500"></center> You can check a site's individual permissions by calling up the Page Info dialog (Command+i on Mac, Ctrl+i on Windows/Linux). Check the Permissions panel and scroll down to "Share the Screen". The current effective permission should have a dot next to it (although it may be grayed out as in my example here): <center><img src="https://user-media-prod-cdn.itsre-sumo.mozilla.net/uploads/images/2020-05-27-17-24-39-a2e47b.png" width="500"></center> If the current effective Permission is Block, change it to Always Ask. If all of that is good, I wonder whether you need to allow screen sharing or Firefox in MacOS settings? Not sure that is applicable to your version.

See also; *https://support.mozilla.org/en-US/kb/screenshare-safety#firefox:mac:fx76

thank you jscher2000