My player has no volume controls! the buttons do nothing!

The volume controls have vanished from the player. The player appears to be muted at all times. pushing the volume up and down buttons turns the screen on, and that is it. the bar that appears at the top of the screen does not come up. i went into the service menu and played around there, but that didn't help. while i was there, i learned that there is nothing wrong with the actual buttons. the 1khz sound that can be played in the menu works in this mode.

notably, when bluetooth is activated, the volume works as normal, but the instant bluetooth is deactivated, it is as it was before.

i really need help with this issue. any help is greatly appreciated.