I have an international HTC One M8, and an off-contract plan with T-Mobile (highest priced, unlimited LTE).
If I go into settings and set mobile data to only use 2G, everything works reliably.
With either 3G or LTE, however, none of my apps can send or receive data most of the time. The notification icon reads "3G". Data is only transferred when it changes to "H+", which almost never happens to me.
What I've done so far:
I've gone into *#*#4636#*#* and switched between LTE/GSM auto, LTE/WCDMA/GSM auto, LTE only, and almost all the rest of them.
I've traveled in the States. I live in Puerto Rico, but I have been to New York, Washington and Baltimore with this phone and SIM card already.
I have tried APNs fast.t-mobile.com, fast.tmobile.com, epc.t-mobile.com, epc.tmobile.com, and even pcweb.tmobile.com.
I have tried combinations of APN types default, hipri, internet, admin, dun, mms, as well as leaving it blank / putting an asterisk.
I'm on a rooted phone with a custom ROM (Carbon), so I tried several different ROMs, both Lollipop- and KitKat-based.
(This is the only reason I haven't talked to T-Mobile reps directly yet, because this still might be an issue with the custom ROMs).
Symptoms are still the same.
Is it a known issue? What can be done?