Pioneer Amp/Receiver VSX-D466S remote malfunction

Question

The unit cannot be controlled with a remote control device. I used the OEM remote and other universal remotes with no success. The OEM remote does control other devices such as the TV and DVD player, but not the amplifier/receiver that it is designed for. I am inclined to think that it might be a malfunction of the internal remote sensor of the unit itself but have no idea how to repair this or to know for sure if that is the problem. I have tried the manual reccomendation of unplugging the unit to eliminate a problem with static interference with no result. I can most likely repair this if I know what part it is I need to buy and where it is located inside the unit. PLEASE advise.

Sincerely with gratitude,
Christine