This is a known problem/glitch.
Apple has, officially, acknowledged and recognized this issue with activation server difficulties with certain iPad models and have stated that they are working on this issue and that it will be resolved as soon as possible.
Hopefully sooner.
It is affecting mostly iPad 2 models, but iPad 3, 4 and 1st gen. iPad Minis are being affected from this, as well.
There are some workaround solutions, but, unfortunately, these do not work for every iDevice affected.
This is clearly an Apple problem/issue that they time to sort out and solve.
Latest Apple news posted, unbelievably, ELSEWHERE other than on Apple's own website/community tech forums.
Apparently Apple has now halted iOS 9.3 updates due to growing Activation Server Lock issues.
Apple halts iOS 9.3 updates for older iDevices due to growing Activation Server Lock issues.