iPad will not shut down when both buttons held down.

Well, to shut an iPad 8th generation down you can:

Press and hold the power button (only that one) until you see the slider to shut it down

or

Go to Settings>General ... scroll down to the very bottom and tap the last option.

Regards

Giulio

You do not have to think about two buttons..

The only button you have to press and hold is the power button.

Regards

Giulio