vpd

I am not a piano player. We got this PX-150 for our sons couple years ago. Now, the note that is the same note as the "Reverb" note is out of tune. It is higher than all the notes around it. I tried the suggestions above and it's not helping. I don't know if there's a factory reset. The manual doesn't clearly explain it. I am at a loss. Does anyone know what else I can try. Thank you!!!