A New Dawn

A New Dawn is a Brotherhood of Steel main quest $$

Detailed walkthrough
Elder Maxson has ordered the Sole Survivor back to the Prydwen for their final debriefing. They are awarded the title of Sentinel and granted a jetpack for their power armor. Maxson informs the Sole Survivor that quests continue to be available at Cambridge Police Station and from Kells. In addition, Reactor Coolant (a request from Proctor Ingram) is now available. The completion of this short quest signals the end of the Brotherhood's main questline, as well as their primary mission in the Commonwealth.

Bugs
Upon returning to the Prydwen, Elder Maxson may be residing in his personal quarters on the main deck rather than the bridge, making it impossible for his dialogue to advance any further, preventing the quest from being able to be completed.
 * This problem can be rectified on PC by going to the bridge and using console commands to move Maxson to the player, use the command in the console to select Maxson, then use the function "moveto player". His dialogue should now proceed normally once he is in the area.
 * There's also a confirmed workaround for the Xbox One if you have a save prior to completion of The Nuclear Option. If you fast-travel immediately to the Prydwen from the roof of Mass Fusion, sprint directly to the Prydwen bridge, then sprint straight to Elder Maxson, it's possible to catch him for the mission dialogue just before he reaches the entry to the main deck, thereby enabling completion.