You should not have changed your Apple ID as that won't help, but will actually complicate your issue.
This is what you need to do. Make sure you have the latest version if iTunes (v12.9.x) running on your home computer, then erase/restore your iPad by following the directions in this link EXACTLY: If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support
If you change your Apple ID, you will need to re-download all the apps on your iPad under the new ID. Apps are forever tied to the Apple ID they were originally downloaded under, so changing your ID was the wrong move.