To put an iPad in recovery mode, force-restart the device by pressing and holding the Sleep and Home buttons for at least 10 seconds. Don’t release the buttons when the Apple logo appears; instead, release them only after accessing the recovery mode screen. Before putting the iPad in recovery mode, connect the device to your computer, and start iTunes.
The purpose of recovery mode is to restore the device to default settings in case iTunes doesn’t recognize it, the Apple logo stays on the screen with no progress bar showing or if the device displays the Connect to iTunes screen. After accessing the recovery mode screen, click on the Update button. This should prompt iTunes to reinstall the iOS operating system again without deleting personal data. The entire process typically takes less than 15 minutes. In case it takes more and the iPad leaves the recovery mode automatically, repeat the steps to put it back in recovery mode, and click on the Restore button instead.
Once the update or restoration process completes, set up the device again by selecting a region, establishing an Internet connection and creating a passcode. If you used iTunes or the iCloud service to back up personal data before restoring the device, select the option to use the backup during the restoration process. If the device doesn’t leave the recovery mode on its own, press and hold the Sleep and Home buttons until the lock screen appears.