Why is my iPad Pro not shutting down with the cover?
The iPad is not shutting don't when cover put over screen
[Re-Titled by Moderator]
iPad Pro, iPadOS 18
Presumably you have a folio cover for your iPad. Not all third-party covers include the required magnet - in the correct location - to operate the iPad's sensor that detects closure of the cover.
Unless your folio cover is explicitly designed for your iPad model - and the manufacturer of the cover explicitly states that it will operate the iPad's auto-lock function - this feature is unlikely to work with your iPad.