In this article, I'm going to cover a possible fix for teachers and staff that have reported not being able to screen-share in Webex. Please note: this is a 'possible' fix, not a guaranteed one. I have seen this work for some people, but not others.
Step 1: After getting into a meeting, locate the 'Participant' menu at the top of your screen.
Step 2: In the 'Participant' menu, make sure the 'Anyone Can Share' option is unchecked. As you can see in my picture, mine is selected. Again, make sure yours is not selected.
Step 3: And that's it! That should fix your screen sharing issue. If not, then your issue is related to something else.