I used to work for cable TV. You wouldn't believe the number of service calls for "no sound" where I'd walk in, turn the knob on the TV, and present a bill for $36.00.(Back when the set top box had a volume control separate from the TV.)

This was after the service desk advised them to check exactly this. Often with a "Look the volume doesn't work, I'm not stupid, send your guy!" conversation on the other end.

1991 Mitsubishi Pajero XP TD LWB family hauler.