Passcode is required to enable Touch ID

This morning I experienced the weirdest thing by my iPhone 6S requiring me to enter my passcode rather than allowing me to use my finger as Touch ID.

My phone was locked probably for like 4 hours while charging overnight and as far as my knowledge my phone did not restart during this time since my Stack Exchange app was left open and upon opening it the same content were still there.

I didn't attempt even once to use my Touch ID; if I would've had a faulty Touch ID sensor then I should've seen such similar behavior either prior to this morning or at least afterwards (I'm already on my phone for the past 3 hours plus).

I didn't register or delete any fingerprints for months.

And finally, I don't have any restrictions setup to require the input of my passcode under Settings > General > Restrictions.

I'm running on iOS Version 10.0 beta 3 (14A5309d)

Anyone out there that has also experienced such similar behavior or with any suggestion on what might've caused it?

With iOS 9, Apple updated the list of times when iPhones will require a passcode rather than Touch ID. The list is now:

• Restarting the device
• Five failed fingerprint recognition attempts
• Receiving a remote lock command via Find My iPhone
• Enrolling new fingerprints in Touch ID
• Not having been unlocked in any fashion in 48 hours
• NEW! When the iPhone or iPad hasn’t been unlocked with its passcode in the previous six days, and Touch ID hasn’t been used to unlock it within the last eight hours

You probably hit the brand new last condition without knowing it. I know you said your phone was charging for only 4 hours, but depending on how long it had been since you actually unlocked, it may still have happened.

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