I cannot install this update 12.4.4, suggestions

The only devices eligible for iOS 12 nowadays are the original iPad Air, and the iPad mini 2 & 3. So unless your device is one of those three, it will not have the option of installing any version of iOS 12. The iPad 4th gen. cannot be updated beyond iOS 10.3.3, and anything else older than an iPad Air2 will be stuck at iOS 9.3.5.

Hello,

You will need to call Apple for assistance.

Contact AppleCare

What happens when you try?

What version of iOS is on the device right now?

~Lyssa