Problem with our remote keeping the code

We are having major issues with our remote for our RCA TV in the living room ... we have a DVR on it also ... we have tried and tried to program it and it might work once or twice and then quits again ... you can turn the TV on with it but it will not control sound or turn it off ... is there another code or codes we can try? Also, we have changed the batteries and that wasn't the problem ...