With the unveiling of the Nexus 6 last Fall, many Android enthusiasts couldn't wait to get their hands on the new phone. It was for the first time, going to be carried at all four of the major U.S. carriers through all retail channels, and would even be carried through the smaller carrier U.S. Cellular. A big part of the excitement of a new Nexus device is the prompt updates to the latest versions of the Android operating system. For those who are using the Nexus 6 on AT&T though, it appears that the carrier is restricting software updates to the device past 5.0 for the time being.
This appears to happen to any Nexus 6 no matter where the device was purchased. So if for example, the user bought a Play Store version of the phone, used it with T-Mobile for a week to test drive their network, received the download package for Android version 5.0.1 but switched to AT&T and inserted their SIM card before they installed it, the software version package gets reverted back to Android 5.0. There isn't any reason we could think of as to why AT&T would be holding back the software update from customers, other than the fact they may have some apps or bloat that they want to go along with the software before they push it out.
According to Android Police, this was tested on a Sprint Nexus 6, where Android version 5.0.1 came in as an available software update, but before it was installed the user inserted an AT&T SIM card. This led them to notice the software package that was previously set at 5.0.1, was reverted back to version 5.0. The good news is that this doesn't really affect many people as you can either re-insert a SIM card from another carrier and be on your merry way, or you can follow one of the handy tutorials we have to flash the factory image of the latest software version that Google has put out. It isn't the end of the world we know, because there are a couple of ways to get around this situation. It is however something that is worth mentioning to our readers who subscribe to AT&T and may have been wondering why they weren't on the latest version of Android yet.