Can't change key
I appear to be having the same problem as this guy from 10 years back, who was told it's a bug:
Perhaps the bug is back or else it's a training issue. But I'm doing just like this user: releasing the mouse onto the pink staff.
I've noticed that it seems to work fine when I craft a new score, enter a few notes, then change the key. So perhaps there is something wrong with this score? Attached. But obviously, Freddie the Freeloader must be converted to Bb!
For what it's worth, this was imported from an XML file that was exported from Sibelius.