Read on below to learn more about a Pokémon Sleep bug notice:

Thank you for playing Pokémon Sleep!
In-game bugs have been fixed.
Bug Areas
Sleep tracking
Bug Contents
A feature can’t be used.
(Occurs under certain conditions.)
Work-Around
This can be dealt with by navigating to the MENU from the title screen and selecting Clear Cache.
Status
Update
The issue has been resolved as of version 2.6.1.
The following gift has been sent to the Gift Boxes of players who were affected by this issue.
• Contents
Poké Biscuit ×3
Sleep point ×100
We sincerely apologize for the inconvenience caused.
We hope you continue to enjoy Pokémon Sleep!
Source: Official Pokémon Sleep news
Source: Pokemon