S2 - Critical
When attempting to add a change of key, the page will not recognize that the key has been changed until the next page. This makes things incredibly difficult especially when dealing with large scores.
Can you attach a sample score and tell how you are adding the key? (drag, double click etc.)
Look at Measure 26, this is where the key change to B-Flat is intended but Musescore will not allow.
In reply to Look at Measure 26, this is… by GastonPH
I believe you because I've seen my share of bugs I can't reproduce, but your Bb is inserted in this file now.
Be sure you are using the official version of MuseScore 3, some of the earlier betas had a bug in this area. The bug that was present before would have gone away if you close and re-open your score, so if a similar issue does still remain, it would make sense you would see it when we don't because by definition we are having to open your score.