Have you rebooted the phone? Try shutting it off, pulling the battery for a few minutes, then starting it up again. Let us know if that helps.
If not, tell us some more about what you've done with the phone. What apps have you installed? Are you rooted? Have you noticed anything else not working correctly?
Are you possibly running a custom ROM? gapps is all the internal android apps that let your phone work with your google account some custom Roms have them outside of the ROM.