Hi,
I had this issue and registered to help you guys out!
I googled and googled since I downloaded the GM, I thought syncing to itunes 11.1 would fix it but it didn't, I came across a forum the other day where someone had posted a quick fix.
http://forums.imore.com/ios-7/25747...beta-1-imessage-facetime-issues-resolved.html
Heres a copy and paste:
Download RedSn0w from the following links:
Mac OSx:
Windows:
Connect your iDevice to the computer with the USB cable
Open RedSn0w
Click on "Extras"
Click on "Even More"
Click on "Deactivate"
Now your iDevice is deactivated and should show an activation screen
Open iTunes on your computer
iTunes should detect that the iDevice is connected and try to activate it
If all is good and apple sends the activation tickets, your iDevice goes back to normal, only this time - with Push Capability.
I did this and it started working without the message straight away, obviously I cannot say whether it will fix it or not for you, so do it at your own risk, but its worked for everyone on that forum.