Can't Update IOS 7 Beta 2 to Beta 3?

I can't update my Iphone 4s which is running IOS 7 Beta 2 to Beta 3. People are Saying its OTA Download (Over The Air) and the update are in the Settings. Well I look in the Settings and I clicked on "Software Update" and i waited there for like 5 minutes. Then it said "Unable to Check For Update". I tried doing it again. And i tried restarting my phone nothing has worked yet. ANY SUGGESTIONS!

You won't be able to update your device unless your UDID is registered. I did mine at http://www.instantudid.com/ for $5. Honestly, it's dangerous to run the beta without having your UDID registered even if you don't update, because you could get bricked at any time.

I have the same issue and have not found an answer that would allow for an OTA install. I would recommend doing a raw download of the.ipsw file and use that to install through itunes as you did for the first beta release you installed.
As for registering your UUID it appears clear that Apple isn't requiring registration for this beta. I have no issues with my device not being registered and neither does anyone else I know with the beta.

Always register your UDID to install a beta to avoid your device being in an unusable state. These guys are always quick and reliable: http://ios6udidactivations.com