There is a mute button but that goes off once you press either the up or down volume buttons. The receiver is connected via coax thru a coax switch to an old 32" SONY Triniton. ( At the other end of the switch is my old VCR.)
Anyways, I connected the receiver to another TV and found out the volume works fine. Hence, the issue is at the TV or connection to the TV - something changed. Darn, and all was working just dandy.
Thank you all for your help, I fixed it at my end. I had a some visitors for the week-end and they finagled with the TV remote and 'accidently pressed' the wrong button.
try entering the fACTORY BIN and start all over from scratch to do the master reset. Double check to see if you have audio on your TV with OTA channels (Exterior Antenna) or maybe DVD player. Also double check the TV also has a mute button