key doesn't work

there's a battery inside. the o/m has instructions to access it, or you can find utube videos

also, the 12v battery can be a culprit

 

This is one i watched.

 

Either replace the battery in the remote or check fuse for door locks, even though if it was a fuse, i think more than door locks wouldnt work

SM-S367VL ?

 

First, where is the spare key remote ?

If you lose them both...or they both go bad.....and you have push-button keyless start.....getting it running again can be VERY expensive.
Like $600 maybe.

It is likely that the battery is just dead in your remote.
Given that you didn't know that, I suggest that you call around to a few locksmiths and find one that works on keyless car remotes and go there and let them help you.

IF....you can hear some clicking coming from the doors when you push the buttons on the remote, the electric actuators in the doors could be going bad. Let's hope it is just a battery in the remote.