Incorrect the MuseScore

I noticed a big error in the MuseScore:
I shifted key and put in the new key signature, but the MuseScore didn't put the natural in the sheet music.

For example:
The key signature was a "b" (Bb), so the key signature was "d" minor. I wanted a modulation to "A" major, so the key signature is three sharp (F sharp, C sharp and G sharp. I put the 3 sharp in the sheet music, but the MuseScore didn't put the natural of "b" (Bb) in the sheet music.

I'm a composer, but it is impossible to compose music with this error in the MuseScore program.
Would you be so kind as to correct this error?
Thank in advance:
Marcell Pethő