Mike has a Google Nexus 6 that isn't updating. He's tried to get Nougat on it, but it won't update. Leo says that the Nexus 6 may not be getting updates anymore, especially through Verizon. Leo says he may have to root the phone to get it updated. Google didn't offer a major update to the Nexus 6, and the security update for March was pulled because it broke Android Pay. They do plan to update to version 7 soon.
Mike can update to Nougat here. Another option is to do a factory reset and see if that frees up the update cycle.