Yesterday media reports flooded the tech world that Apple's iOS 9.3 release was causing upgrade errors. Specifically, some users could not activate their iPhones, iPads, or iPod touch devices after installing iOS 9.3
According to Apple, updating some iOS devices (iPhone 5s and earlier and iPad Air and earlier) to iOS 9.3 can require entering the Apple ID and password used to set up the device in order to complete the software update.
Apple has released another build of iOS 9.3 specifically for the iPad 2 to eliminate the activation bug. Once that's been downloaded and installed, Apple's aging tablet should function normally once again. However, in order to install this one you'll need a computer, and Apple's also installing the updated iOS 9.3 build at its retail stores.
For those who can't recall their passwords or can't sign in, Apple is offering a workaround. Apple suggested that users remove the activation lock by signing into their iCloud account's Find My Phone function or by connecting their device to a computer and entering their current Apple ID details into iTunes.
If you are still facing issues, espacially with your iPad 2,you can read this support page or contact Apple's support.