iPad 2 can be updated to iOS 9.3 without activation error
Apple has finally released a modified version of iOS 9.3 build 12E236 for iPad 2 to fix update issue.
New build 12E236 of iOS 9.3 solved activation problem that appeared after updating iPad 2 to iOS 9.3 build 12E233.
If you haven’t updated yet to iOS 9.3 feel free to do it.
If you have bricked iPad because of activation error don’t fear to update your iPad once again. Try it again via iTunes.
But before that make sure that you have the latest version ot iTunes software on your PC or Mac.
There is an option to update to iOS 9.3 by restoring iPad 2 in iTunes using previously downloaded iOS 9.3 build 13E236.
Here is a direct link to iOS 9.3 build 13E236.
P.S. Have you updated to ios 9.3 using this help? Let us know about it in comments.