Screen share - only half the class can see

While teaching a group of 12 students, the professor shares his screen in Teams. (I'm the assistant)  Half the class can see the slides he's sharing, and the other half sees a black screen.  The professor exited screen share and then reshared.  That time, a different group of students could see and others couldn't.  He stopped sharing and started sharing repeatedly, but never got to a point where everyone could see the screen.

The professor and students exited the meeting and rejoined but the problem persists.  We still have 2 more hours of class and 50% can't see the slides.  Now what?