Does your remote look like this?

If yours varies from this too much, you've got the wrong one.
If you do have one like this..Does it look beat up? You could have a bad fob. Just because you bought a car with the fob, doesn't mean that everything is all good unless everything came to you new.
Have you done the normal curious thing that most do? Have you taken it apart and checked the battery contacts, the board, the buttons? If so, have you thought about getting a new one?