Do you only have 1 remote programmed? (2 remotes came with the vehicle when sold new).
If you have access to the 2nd remote, see if the vehicle responds - you might just need a new battery in that non-functional remote.
If neither respond, you can test the batteries if you have a multimeter/battery tester.
If the batteries are good and you haven't dropped the remote(s) in water to damage them, you may want to bring the vehicle into your local dealer and have them check out your vehicle's keyless receiver.