Slide Control not showing even after Settings has been updated

Having the same issue and it's intermittent.  2 weeks ago it worked perfectly, now it's not, and I haven't changed any settings.  Slide Control button appears as normal at the top and when clicked shows all of my participants in the drop-down, but will not allow me to select anyone.  Had to use Remote Control, which is horribly frustrating and inconvenient since I cannot do anything, such as reply to Chat, while my cohost is facilitating. 

I have the same problem. Very difficult when hosting a webinar.