Treazor

Hello, I have a casio privia px-120 and i use for my church worship practice at home and suddenly one day i was using and i left it on and when came back to play, it had low volume even when I turn the volume up. I have tried to switch it off and on but nothing has changed. Its stills remain at a low volume like really low. I have e tried the manual but nothing works. Can you help? Thank you