The message indicates that Screen Sharing is Paused. The contents of the orange box you see is just a mini-view of what you are sharing. You should see the green arrow Resume Share button which will take your screen share "Live" again:
I'm not sure why your screen share went into "Pause" mode - probably an accidental click. But if it happens again, click the Resume Share button and you'll be fine.
The problem only seems to happen when I try to go full screen from a YouTube video I'm trying to share, using the little full screen icon at the lower right of the YouTube window. Up to that point, all is fine.