You can check to see if the remote is sending a signal by looking at the LED emitters with a digital camera. I use a cell phone camera. If the volume buttons emit IR in both receiver mode and DVR/TV modes, then probably the remote's buttons are OK. However, also make sure that when the remote is in receiver mode, that it doesn't control the TV or DVR (which would be caused by the receiver mode button not working, and leaving the remote in the previous mode.)

Another possibility is the receiver is not responding to IR signals. Do you have a universal remote (e.g. cable or satellite) which can control some functions on the receiver?