I had the same problem. I seem to have fixed it by going into settings and forcing data network to use 3g leaving settings browsing Web, then going into settings again and choosing LTE.Unfortunately I am not a dev. A few years back I started down the dev road, but kids and work have squashed my dreams ATM. There is a logcat posted from @Ventigo http://forum.xda-developers.com/showthread.php?p=67418271.
I'm just curious if the device tree has an old firmware version in it and needs to be updated. Hoping someone else posts here that is working and we can track down if this is the culprit. I can't get a single ROM to get past this phone.android.com message.[emoji37]
As far as the AT&T data, mine is working just fine. I have both T-Mobile and AT&T Sims and both can pull data. Maybe just the area your in?
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