I've had this problem on and off for many months. When I'm away from WiFi sometimes I will have a good strength cell signal but no data. My wife has the same phone as me - the HTC One M8 (both purchased from Ting) - and hers has a good data connection. I have tried updating the Profile and PRL and they did not help. I called Ting about this and they suggested doing a carrier reset, by dialing ##72786# and selecting Menu -> Reset. This worked well and got my data connection back (after waiting a while for the phone to reboot and re-activate). The problem is that it will only last a few days and then I have to go through that whole process again. I have had several times where I have my phone on the table and no data connection, but if I do the carrier reset procedure and wait several minutes for the phone to reboot and reactivate, then I have a working data connection again without moving the phone at all. I even tried factory resetting my phone and setting it up again to see if this problem would go away but even after the fresh Android factory reset I still have the same problem. I'm not sure what would be different between my wife's phone and mine that would cause this different behavior. Is there anything else I can try?
Keep losing mobile data connection and having to carrier reset on HTC One M8