Read on below to learn more about Pokémon Sleep:

Notice: Maintenance

Thank you for playing Pokémon Sleep!
In order to improve the stability of the game, maintenance will be conducted in the following time frame:
We apologize for the inconvenience and appreciate your cooperation.
(You can still track your sleep during maintenance.)

Maintenance Period

Starts:2023/7/24 19:00
Ends:2023/7/24 23:30

Source: Official Pokémon Sleep news