Why can't I share my screen or window?
Are participants reporting problems when trying to view your shared window or screen? This article might help.
When sharing from a Windows PC, your participants see only a black screen and your cursor.
Most likely you are sharing a window that is running with elevated privileges (that is, it's being "Run as administrator").
You must run join.me with elevated privileges, as well.
To run join.me with elevated privileges, right-click the join.me icon and select Run as administrator.