I have a Nexus 6P running CyanogenMod 13.0-20160819-SNAPSHOT-ZNH5YAO0IN-angler based on Android 6.0.1. I used to be running a CM nightly build and my cell carrier is Ting. Here's what happened:
I was running a CM nightly build from March-ish for a while. A couple days ago, I upgraded to the latest CM nightly. Immediately after that my WiFi stopped being able to find/connect to networks, and a day or so after the upgrade my cell network data connection stopped working. (SMS and phone calls worked, however.)
I decided to switch to a CyanogenMod snapshot release, so I factory reset the phone and flashed CM and gapps (at the same time). I wen through the setup and lo and behold, the problem appeared fixed. However, when I restored all my stuff via oandbackup (including, I now realize, some system apps), the problem reappeared.
Thinking that there was somehow some system app with corrupted data that I'd now restored, I used oandbackup again (along with a TWRP backup) and factory reset again. I went through the setup, planning to simply restore apps one by one until I found the culprit, but the freshly-setup install had the same problem. Therefore I restored the TWRP backup, which brings us to now.
So, why can't I connect to data? Most of the time this problem causes the cell indicator in the status bar to have a "!" however sometimes it shows just the bars, without a "!" or the "LTE" indicator. I believe this behavior occurs when the phone is first booted and goes away for the remainder of the boot when Airplane Mode is toggled, but I can't confirm for sure.
Here's what hasn't worked:
- Wiping Dalvik cache
- Trying most of the APNs, toggling Airplane Mode in-between
- Restoring the default APN settings
- Selecting a network operator (there used to be two or so "Ting" entries available; I only tried one - now nothing shows up at all)
- Selecting "choose automatically" in the Network operators settings
- Toggling the preferred network type to 3G and back to LTE (toggling to 3G caused everything but the status indicator bars [i.e. the "!" and "LTE"] to go to away; I suspect Ting simply doesn't have 3G available anymore)
- Turning on Data Roaming and toggling Airplane Mode
- Downloading a factory image from Google and running
flash-all.sh(i.e. flashing stock recovery, system, radio, etc.)
ADB logs of me booting my phone to the launcher and waiting a couple seconds for it to connect to the cell network: https://gist.github.com/strugee/cd61dbcc461bb17216c360516e711d29