FWIW, here's a bug report and workaround. If you select a clef, do control-e to edit it, and change the clef, the key signature won't change to reflect the new clef. I know this a bug and not a feature, since the help claims that the key signature does change along with the clef.
The workaround is change the clef as above, then select the incorrect key signature, cut and paste it. After the paste it will be correct.
There's another fix for this:
Press F9 (Refresh Score).
Tim Reichard