Apple has today released a new version of iOS 9.3. This comes a few days after the launch of the new version. With that update came some issues for users who needed to activate their device via iCloud and could not remember their password. After an update, the device is not supposed to ask to be activated, just an optional login screen.
If you are on an iPhone 5s or older or iPad Air or older, you can download the new build of iOS 9.3. Apple has also started signing this version again, allowing it to be installed. If you installed the update and could not sign in, you can manually install the update via iTunes and you will be able to skip the login. Otherwise, go to Settings > General > Software update > iOS 9.3 to download and install the new build.