Only one participant did not have share screen button

[Katrinalee14]

I was hosting a zoom help desk for family history with screen sharing enabled for all participants. Someone joined the zoom help desk but seemed to not have a share screen button. He read me all the buttons across the bottom of the window, "chat, reactions," etc., as well as the "more" button topics. No green share screen button. 

He was using a new Macbook. He was a first time Zoom user. 

Is this even possible?

How can we fix this?

Thank you.