Pokémon Sleep maintenance has officially wrapped up as of today, Jan. 15, restoring full access to the app after the recent downtime. Players can once again start tracking sleep, complete research and use all features without interruption. The maintenance supported the rollout of version 3.2.0, which includes behind-the-scenes updates and improvements. If you held off on starting a sleep session during the downtime, it is now safe to jump back in and resume your regular routine.
Source: Official Pokémon Sleep news
Pokémon Blog 