Does your case have a hole in it, to allow your finger to completely touch the fingerprint scanner? Like it's not obstructed or has a plastic window in it.

 

I can use the tip of my finger on my FPS.
Did you register your entire finger? (Just saying).

Lateck,

 

Try re-registering your fingerprint with the phone in the case.

 

Check to see if you have an update. verizon pushed an update where you dont need to touch the metal band anymore for the scanner to work. my theory is it was a security idea from LG to make sure YOU had to be the one unlocking your phone

 

I just got this case today (picture below has slots on the side that expose the metal sides):



Fingerprint scanner works flawlessly (even without redoing my fingerprints). Its Urban Armor Gear:

http://www.urbanarmorgear.com/collections/lg-v10-cases

 

I also have this case but in clear. I like it. It is strong but not heavy. It is cheaper in other sites. I do not recomend to buy it from manufacturer directly