Originally Posted by
Robborboy Ah, did you flash an unbranded ROM? That may very well be the trick. I didn't even think of that.
I re-flashed the ROM that was meant for that phone because its quicker and more reliable than having the phone update OTA.
But Internet Sharing works on the AT&T ROM with no extra effort, as long as it's running windows phone 8.1 and above. (dev preview works, we'll see about denim)
AT&T locks down their phones anyway so you cant flash them with anything but AT&T firmware.