Could be any number of things:
- Basic remotes shipped with electronics gear are cheap and have very poor IR signal strength. You could try changing the distance between you and the dvd player and the angle between you and the player. If it still doesn't work when you are right in front of the player facing dead on then something else is the issue.
- Does the remote have learning capabilities or at least offers pre-programmed setup codes to control other equipment? If so, you must make sure that the remote is in 'dvd' mode so it is sending dvd commands.
- Does the manufacturer of the dvd player make other components as well? If so, the remote may have the ability to send an ID as part of the remote code so as not to conflict with other equipment that would respond to the same codes. If the ID doesn't match the player will not respond. Look in the manual to see what the default ID for the player is and what the ID of the remote is set to by default. The manual should describe the procedure to change the player and remote ID code so they match.
- Maybe it is the wrong remote for that particular player? (hard to believe if you bought it new but you never know).
- Interference that would alter the IR signal, like overhead flourescent lights? Turn them off and try again to see if that is the issue.
- Anything in the way of the IR sensor on the player that would impede IR signals, like wood cabinets or darkly tinted or smoked glass of an entertainment center?
Lastly, it just may well be a defective remote or the IR sensor of the player is not functioning properly.
