Roland KR-4700 Volume Barely Audible

I recently acquired a brand new Roland KR-4700 digital piano and the audio is barely audible. The speakers test fine with a multimeter and the capacitors look like they’re in good shape. Not quite sure what else it would be, as the volume slider does work, it is just very quiet even at the max volume. I have included a picture of the the schematic. Any help is very much appreciated. Thank you!