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.

Thanks for response.
Looks like DAC parts are dead.
I ordered digital to 5.1 analog signal converter. Hope it would work, even with sound quality degrade.

The digital to 5.1 converter, with the 6.1 channel input from the receiver, worked just fine. It cost me $60 for the converter and I guess I can save the Yamaha receiver for a while.