I just faced this problem.. i turned on my VPN last night and a pop up told me to change my lockscreen settings to either password or fingerprint (I'm using Samsung Galaxy Note 4), so i did. Ever since that, I cant change my lock screen settings back to none.. i have tried deleting all my VPN. I have tried to choose the Clear Credentials option but its grayed out. I have tried entering my google account at the forgot password section on the lockscreen but it shows that i had entered incorrect username or password (but I'm sure of my google account email and password). So what else can i do?