Q: Unable to activate ipad following ios update

Read here:

If you can't activate your iPhone, iPad, or iPod touch after installing iOS 9.3 - Apple Support

Contact Apple support then:

https://getsupport.apple.com

Seems like Apple has temporary  troubles with their activation servers. Lots of users report similar issue on older devices.

https://support.apple.com/en-us/HT206203

Recent info  : If you can't activate your iPhone, iPad, or iPod touch after installing iOS 9.3 - Apple Support

http://www.imore.com/apple-working-ios-93-fix-older-iphone-ipad?utm_medium=slide r&utm_campaign=navigation&utm_source=im

Hoppefully Apple will shed the light on it soon.

Have you seen this yet?

http://9to5mac.com/2016/03/24/apple-releases-new-build-of-ios-9-3-for-users-of-o lder-ios-devices-affected-by-bricking-bu…

It was posted earlier by bobseufert