FaceTime not working, iPhone 4 iOS 7.1

FaceTime is not working. I keep receiving the message: "An error occurred during activation. Please try again." This is within a few seconds of attempting activation. It doesn't accept my Apple ID either, and FaceTime doesn't even show up under General Usage. iMessage doesn't work either, although it is still in General Usage. I never attempted to delete either one, have reinitialised my internet settings and restarted several times.