Chosen Solution

Denon RC-977 remote. The unit(AVR-1795) won’t turn on or of by the remote. AVR-1705 is on, on standby. Yesterday, the sound could be controlled, but now, that won’t work, either. The red light(transmit signal indicator?) stays on all the time.

It could be that the remote control batteries are low. Replace the batteries and see if it works. Another reason could be that the electronics inside the remote may need to be reset. This is done by removing the batteries for a couple of minutes and then putting them back in place (if the batteries are not exhausted). Mind battery polarities.