Even if the solder joints on those parts i mentioned in my previous post look fine, resolder them anyway. Don’t add anymore solder just heat them up until they flow onto the pad. We call it “reflowing” the solder joints. Sometimes it’s easier to reflow all of them than try to trace out the single bad joint. Also make sure that all of those components are in the correct place and nothing is switched. Since you said the volume control has no effect on the sound then it must be in the signal path after pot VR9. Look very closely at all the solder joints around the audio amp ic U3, make sure nothing is bridged…use a magnifying glass if you need to. Good luck. Let me know what you find.
-Brach