I had the same problem at first. AT&T said they were waiting on an update from Microsoft, but nothing seemed to be happening.
I then told them to "disable my internet sharing on their end." Then I asked them to re-enable it. Problem solved. Once they turned it off and on for my service, it reset and all was good again.
I'm not saying it will work for anyone else, but you know how finicky Windows can be. Have to shut down and reboot once in a while. :)
Lumia 520, problem occurred after upgrade to 8.1/Cyan.
09-11-2014 02:20 PM