Trouble sharing your screen or a window?
Black screen during window sharingSymptom
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").
join.me must be running with elevated privileges, as well.
To run join.me with elevated privileges, right-click on the join.me icon and select Run as administrator.