"Share Screen" icon not visible

[DMG]

Today I invited my mother to her first Zoom meeting.  One problem we found is that there was no "Share Screen" icon on her computer.  What could be causing this and how can we fix it?

She did have icons "Settings" and "More" that were not visible in my window.   

the related settings in my account are

• Screen Sharing: Enabled
  Who can share? All participants
• Who can start sharing when someone else is sharing?  Host only
• Show a "Join from your browser" link: Disabled

She is running MacOS Catalina.

[DMG]

More information: she did not have Zoom installed, so was joining the meeting through the Safari browser.  I had her download the Zoom app, and had her use that, but the "Share Screen" icon was still not visible.  Note that she is not a fluent computer user, so I can only assume that after downloading the app that she was joining the meeting using the app and not using the browser.

[SAllyM]

Having the same issue--no "share screen" icon.  I am a "basic' user on a MacBook Air and was acting as meeting host.  I have deleted and reinstalled Zoom several times, opened privacy and security settings to allow for video and microphone and followed several help videos to no avail.