If your iPad has not already been successfully updated to iPadOS 16.7.x - and is capable of update to iPadOS 17.x - you'll not be able to update to iPadOS 16.7.2.
As of last week, the only upgrade path for any iPad capable of update to iPadOS 17.x is to update to iPadOS 17.1.2. A downloaded but not yet installed version of iPadOS 16.7.2 will not be verified. This update package, if it still exists, must be deleted from your iPad.
Settings > General > iPad Storage
Scroll down the list of Apps to find the update package - tap - then select Delete Update
Close the settings App - and then restart your iPad:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)
Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.

After restart, you'll be able to install iPadOS 17.1.2.