Car key remote fobs are nice to have, but they all stop working eventually. Even if it's just a dead battery, you can pretty much guarantee that your car doors will fail to unlock with the remote at one time or another.
While there are a few reasons that a keyless entry remote might stop working, most of them are pretty easy to check yourself. The most common problem with these car key fobs is that the batteries go dead over time, in which case replacing the battery should fix the problem.
Other key fob remote problems are more complicated, but it's still possible to fix them.