It looks like AT&T or Moviebox has stopped the ability to stream via 3G, 4G, LTE over any AT&T network. We have came across people having the problem if their home internet is supplied by AT&T. So we have look into it, and found if you use a VPN you can get back going. Yes the VPN is slower, but it works. A few app that we found that work and are in the App Store are.
Hotspot Shield VPN
Some are free and some have in app purchases. The best one that we found was the VPN Unlimited.