Most likely a bug with the apple servers. i've had this problem on beta 1, but i suggest you upgrade to the GM (final version) because ios 6 beta will expire at any moment. here is a link to my thread Forums/t=5662880/ios-7-golden-mas...vices.html

No risk of expiration, it is the version that will be released next week.

whats expiration ? im new loooool

I recommend logging in and out of your iTunes account in your settings. That's what I did and it fixed the issue when I had it in beta 3.

expiration date. means it wont go bad (in simple terms)

Does your iPhone say waiting or activation? In that case you might have restored instead of updated when getting iOS, if your still having this problem but your device into restore mode manually
(Turn off >>Hold sleep button 5 seconds>>Hold sleep and home button until the icon appears on your iPhone screen!>>restore via iTunes!)
GOOD LUCK!

by expiration he means they`ll shut down the servers and if you wont that to go away you can have your UDID registered like me but i would just wait 3 more days till it comes out because i doubt theres gonna be ios 8 in a year

just wait till the public release comes out its only 3 days