I have a really stupid suggestion and I am not in any way making any type of comment on one's intelligence or technical capability. I know a guy whose left channel went out on a brand new, not inexpensive, McIntosh setup. He was kinda pissed and laid into the dealer who kept telling him this isn't possible. My friend changed the cables from one channel to the other and confirmed the left one was not working.
After a bunch of back and forth, the dealer paid a house call to see the problem for himself. He took the remote, pushed buttons to get to the channel balance function, saw it was 100% over to the right channel, rebalanced for both channels and WOW! music came out of both channels. Kind of embarrassing, to my friend 😯
Have you checked your channel balance function? May save you a house call cost 😏