For reasons unknown, AT&T has just suspended the rollout of Android 5.1 to the first generation Moto X. Motorola announced the update last month, and it first began rolling out to AT&T Moto X (2013) owners on July 7th.
Here’s what AT&T says on its support website:
Effective July 20, 2015, the Android 5.1 (Lollipop) software update for the Moto X (XT1058) has been temporarily suspended. We apologize for any inconvenience and are working to resolve this issue as quickly as possible.
As mentioned, it’s not yet clear why AT&T has pulled the update for now. The company does say that it is working to resolve the issue as soon as it can, and the rollout should continue soon.