Help: right channel not working on Yamaha rx-v3000

With further testing, I've found out the receiver does not work for all digital inputs, but it works for analog input. That is, if I play my CD player with RCA jacks, the receiver works for both inputs, but with digital connection, the right channel does not work.
At least I can use it for 2 channel receiver, but it would be nice if the problem is simple enough for me to fix it.

Ihcho,
If it works for the rca input and plays at the speakers, that eliminates a blown output channel, which is good. My guess is that it may be a bad digital cable. Some, especially early, digital cables were fiber optic and contained glass internally. These types of cables cannot be bent or crimped since it will break the glass inside.
This is easy enough to check by just swapping out your cable for another.
If that doesn't work, you may need to bring it in for service and have them check it out internally.Hope it's just a cable, good luck.

Maybe the dac is ready for a retire.

Have you try unplug it from the AC outlet for a minute to reset the processor?