Htc One m7 will not update! HELP!

I've been trying to update my HTC One for months now to Android 4.4, but each the phone searches for updates it says no update is found. I know I'm properly searching for the updates through the settings, so that's not a problem. I've also tried setting the date forward. Nothing seems to work. Does this have anything to do with me having at&t's GoPhone service instead of a contract? If so, do I have any options updating it without being on a contract (i.e unlocking phone)?