Screen Sharing - Recently my normal function to Share screen stopped.

Hi Guys, recently, my normal process to share screen stopped.

All functionality and links were checked – all correct. I then tried sharing screen before someone entered the room – was sharing and then stopped as soon as person entered the room.  Is there anything I'm missing or need to do? 

I've registered with Help support –no reply thus far, and I have also escalated a ticket request.

I'm really needing an answer asap, please for big meetings tomorrow.