Q: I can not activate the ipad I have tried restore and that does not work

Read here:

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

What has serial number got to do here?

Read about Apple ID below:

iCloud: Apple ID

re start your ipad by pressing power and home button,when apple logo appear release the power button while continously hold the home button,the connect to itunes logo will appear,then connect your ipad to your laptop/itunes,your computer will do the rest.it works for me,,,,

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.