Passcode Requirement

Was iPhone repaired before?

What were you doing when the prompt appeared?

Is your Touch ID not working?

After setting up Touch ID, there are two ways to unlock your device:

• Wake up your device by pressing the Home button or the Sleep/Wake button once. Then, touch your finger lightly on the Home button to unlock. If you reach the passcode-entry screen accidentally, you can still use Touch ID to unlock your device.
• Wake up your device and slide to unlock it. Then enter your passcode.

To configure Touch ID, you must first set up a passcode. Touch ID is designed to minimize the input of your passcode; but your passcode will be needed for additional security validation:

• After restarting your device
• When more than 48 hours have elapsed from the last time you unlocked your device
• To enter the Touch ID & Passcode setting

Try

Force Restart

http://support.apple.com/en-us/HT201559

Note: You will need to use the passcode after the above.

You're welcome.

A C&P is appropriate here...

If it has NEVER been jailbroke, here are some standard repair procedures:

First, try a system reset. It cures many ills and it's quick, easy and harmless...

Hold down the on/off switch and the Home button simultaneously until you see the Apple logo. Ignore the "Slide to power off" text if it appears. You will not lose any apps, data, music, movies, settings, etc.

If the Reset doesn't work, try a Restore. Note that it's nowhere near as quick as a Reset. It could take well over an hour! Connect via cable to the computer that you use for sync. From iTunes, select the iPad/iPod/iPhone and then select the Summary tab. Follow the on-screen directions for Restore and be sure to say "yes" to the backup. You will be warned that all data (apps, music, movies, etc.) will be erased but, as the Restore finishes, you will be asked if you wish the contents of the backup to be copied to the iPad/iPod/iPhone. Again, say "yes."

At the end of the basic Restore, you will be asked if you wish to sync the iPad/iPod/iPhone. As before, say "yes." Note that that sync selection will disappear and the Restore will end if you do not respond within a reasonable time. If that happens, only the apps that are part of the IOS will appear on your device. Corrective action is simple - choose manual "Sync" from the bottom right of iTunes.

If you're unable to do the Restore (or it doesn't help), go into Recovery Mode per the instructions here. You WILL lose all of your data (game scores, etc,) but, for the most part, you can redownload apps and music without being charged again. Also, read this.