I finally got my iPad2 64gb wifi+3g working again with these instructions:
https://support.apple.com/en-us/HT206214
Not sure if necessary, but before I took the steps described, in iTunes I checked for new versions in the iTunes main menu. It found a new version of IOS9.3 released today and downloaded it.
One other thing I did first was disconnect Wifi and delete the iPad in iCloud.com > settings (under account top right) > my devices.
Then I took the steps in the Apple support document.
As described after about 15 minutes there is a timeout and you have to do step 3 again.
It got through the update process the 2nd time.
Then I got a message in iTunes that my simcard needed a password, but nowhere to enter it. So I was stuck again. I then unplugged the iPad, removed the simcard and plugged the iPad in again. Then the process could finish, you have to enter your Apple ID on the iPad an all was working again.
So before taking above steps, remove your simcard.
I now have a fully working iPad2 again with IOS9.3. I lost nothing, I did not have to restore a backup.