Q: new iOS 9.3 problem

  Restart your device and try one more time. Servers may be overloaded at the moment. This won't delete your data stored on this device.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Also check this link If you can't activate your iPhone - Apple Support

IF you look around this forum, there are many iPad 2 users making the very same claim. Try connecting the iPad to iTunes on your computer and see if you can activate that way or take a look at this and see if this works for you. This will erase the device, so hopefully you can backup first.

If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support