How can I adjust my iPad sleep time when auto-lock is grayed

iPad auto-lock will be fixed at two minutes if you have enabled Low Power mode:

Settings > Battery > Low Power Mode

If the problem persists after disabling Low Power Mode, perform a forced-restart of 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:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. 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.

You might also check that Date & Time and TimeZone are also correctly set for your iPad - as these settings are known to cause various functional issues if incorrectly configured:

Settings > General > Date & Time

If you have a work or school email account on your phone, or it is under MDM, the administrator can block access to that setting and create a default value for it.

You're very welcome. I'm delighted that your problem was easily identified and resolved.