My iPad 9th generation turned off and will not restart

If your iPad is unresponsive, connect your iPad to its Power Adapter and allow the iPad to charge undisturbed for at least and hour - or preferably overnight. Then, while still connected to external power, try a forced-restart:

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.

If iPad still doesn’t turn on, or if it gets stuck during start up, see the Apple Support article If your iPhone, iPad, or iPod touch won’t turn on or is frozen. Or if your iPad isn’t working correctly after you restart it, see the iPad Support website.

If you continue to experience difficulties, you might be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively, you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad:

Genius Bar Reservation and Apple Support Options - Apple

What the tech told you is horsehockey. They certainly can do more than that, up to and including repairing or replacing the iPad. My guess is that the tech either is poorly trained (not at all uncommon at Best Buy) or just doesn't want to deal with it. Contact Apple Support and talk to them about the situation. They may be able to offer mail-in service, or they may be able to put pressure on Best Buy to give you proper service.

Regards.

Take the iPad to an Apple Store or authorized Apple service center for evaluation.

Regards.