I have Windows 10 laptop running Chrome. When trying to share a PowerPoint presentation only the first slide is transmitted when PowerPoint is in the slide show mode. In any other Powerpoint mode the screen sharing seems to work fine.
This is a browser issue and there is nothing we can do about it. You may try changing the browser and see how it goes.
These issues need to be reported at the browser’s issue tracker.
Fwiw…The behaviour is same with Brave and Firefox too…