Q: Fingerprint grayed out in settings

You need to "Turn Passcode On" and then add a passcode.  Touch ID will not be avaialble unless there is a passcode in effect.

I actually ran into this same issue.  My passcode is turn on and enabled, but the Touch ID is still grayed out.  Did a soft reset and still the nothing.  Any suggestions? 

Having the same issue as described by "edward 46".

My ended up being a faulty hardware issue on the scanner.  Apple had to replace my phone. 

I fixed a friends by discovering that the Apple ID that the phone was signed into did not have a credit card verified to it therefore the setting was greyed out, it had nothing to charge to when using touch id to purchase apps. Check your iTunes payment details in settings>store etc..

Go to Settings> iTunes and App Store.

Sign out of your account.

Sign back in then go back to Settings > General > Passcode and Touch ID and you should be able to turn it back on.

Dib.

That doesn't work either

I had the same problem and it turned out that my credit card on the payment information wasn't verified. I corrected it, restarted the phone and....Bob's your uncle