After a few days of data connectivity hell for some Nexus 6 owners, it seems that Google corrected the issue on the back end. Comments on a post in the r/Nexus6 subreddit indicate that most people have had their LTE data connection restored by this fix; however, many are reporting that they addressed it themselves by changing the APN settings or by updating their Google Connectivity Services through the Play Store.
As of now, it is unclear how exactly the issue was solved, but a Google employee named Orrin (u/GoogleNexusCM) posted an update on both r/Nexus6 and the Nexus Help Forum on Google's Product Forums. Orrin explained that the data outage was caused by a problem with GPS, although he didn't go in depth.
It seems like most owners affected are on T-Mobile, but there are a few reports of issues from people on other carriers.
If you're a Nexus 6 owner and you're still having issues, perform a restart on your device.
- Google Product Forums