When Apple released iOS 9.3 there have been some notable bugs that have created issues for some users after they installed the latest update. The main issue was with iPad Air and earlier models required entering the Apple ID and password to used to set-up the device to complete the software installation. If for some reason, iPad owners couldn’t remember their password, their devices were stuck in an inactivated state until they could either recall the password or were able to reset it. As a result, Apple temporarily disabled updates for the older iPads (and iPhones older the the 5s) until they could release an updated version of iOS 9.3 that didn’t create the same issues. Apple has created a support document for those iPad owners who are currently stuck in the activation state.
If your iPad will not install the update after downloading it,or displays the message your iPad could not be activated because the activation service is temporarily unavailable you can try connecting it to any computer with the latest version of iTunes installed and update.
Once connected to a computer, open iTunes. Next, force your computer to restart by pressing and holding the Home button at the same time as the Sleep/Wake button. Keep holding this button combination until your iPad goes into recovery mode. The screen will look like this
You will now be presented the option to restore the iPad, or update the operating system–choose update. By updating the iPad, all your settings and content will remain untouched, while the latest version of iOS is installed. At this time iTunes will take up to 15 minutes to attempt to reinstall the latest version of iOS without erasing your data. Once the update finishes, you will have to leave your iPad connected to your computer and finish the activation process.
What else can you do?
If that doesn’t work, or if you haven’t yet tried to connect to iTunes to update your iPad, Apple has just released 9.3.1. This update was intended to address another bug that fixes an issue that caused apps to be unresponsive after tapping links in Safari and other apps. However, when my iPad 3 would get stuck in the activation sequence, updating to 9.3.1 fixed the issue in the first attempt.