Got my phone in late August, and it always worked well with Google fi, autodetecting the apn. To be fair, the apn that is listed is correct, mobile data is just not working. I can tell it worked up until just a few days ago, and I did the 1AMD update long before that. Really no changes were made that I know of except for possibly having the phone on a wireless charger overnight. It was hot.
Chiming back in on my last post, a master reset fixed it. No clue what had happened where it stopped working.