If you play a Concert instrument (like piano, guitar, flute) the key you choose in Player controls, should show the chords in that same key.
If you play a transposing instrument, it should be showing the correct transposition from Concert key which you choose in Player controls and the visual key you see your chords in for your instrument.
However if a song has been entered incorrectly, the chords will be showing in one key, but the key set for the song is different. There is a mismatch. No matter what you transpose the song to, it is showing the chords in a different key than expected, whether you play a concert instrument or transposing instrument.
Open the song in the editor
iOS, Android: tap on 'i' (Song info) button, choose the key the chords are in then tap "Set";
Mac, Windows: select the key (at the bottom of the editor panel) the chords are in, and click "Set"
The Default key signature of the song will be changed – without changing any of the chords. The default key you have set for the song should then correspond to the chords as they show in the song editor.
Example:
You have a song showing chords based in C but the default key signature shows D when you open the editor. Choose C as the key, tap/click "Set".