I can not share my screen in some meetings

I am unable to share my screen in some meetings.  But this seems to be an issue only for me.  Everyone else in the meeting can share.  I have checked all the settings with the meeting host and the other related questions in this forum.  

It seems to be a problem just for me.

• I don't have a screen sharing option on my screen. 
  • I see this message when I join the meeting 
    •  
    • Your are restricted from sharing in this meeting
• *All* other meeting participants can share (logged in or guest).  
• I am even the meeting co-host.
• If i start a new meeting I can share my video in that meeting

What could be wrong? What have i missed? I have the latest version of Zoom. And as near as I can tell all the settings are correct ... but something is causing this strange interaction.

(By the way I have an older MacBook and this used to work.)

Cheers,

Steve