I had a (perhaps) similar experience after returning from a long trip & switching all my gear back on.
I thought my 861v8 was toast...

But simply (physically) unplugging the power, disconnecting the DSP's, and then slowly reconnecting everything fixed it.

I've also had scenarios where, again after the power being off after a long trip, one of the inputs either doesn't work at all (silent) or is very quiet / muted. Power off - at the switch - and physically unplugging / re-seating cables usually seems to do the trick.

Trinnov Altitude CI-12; Meridian 861v8 + ID41 + UHD722v2 + 271, 2*SE-update DSP8.2Ks, SE-update DSP7200HC, 4*DSP3200, 4*DSP33, 218, 251
JVC DLA-NZ8; Panasonic TX-P60ZT60E; Lumagen Radiance Pro 5348
Roon [13i7 Win.11 NUC]; SKY Q; Oppo UDP-203EU; AppleTV / Fire Cube / Roku / NVidia