When trying to take a snapshot screen turns gray and cursor has a white teardrop attached to it. Therefore it will not take a screenshot

I use Take a Snapshot to make mailing labels.  Today this option isn’t working.  When I select Tak and Snapshot screen turns gray and cursor is followed by a white teardrop.  If you try and select the label address it makes a white box which disappears as soon as I let go.  Obviously have something set wrong, just don’t know what.  Have tried rebooting multiple times.