Second login screen has me locked out
I have just encountered this issue. The way that worked for me is to reboot into single user mode and create a new administrator as described here http://www.hackmac.org/tutorials/how-to-create-a-new-administrator-account/ then use the new administrator to reset the original accounts password. Then I was able to log into the original account.

Before this method, I have tried


resetting pram and smc
running disk check from recovery mode
unsuccessfully trying to modify the encrypted apfs to decrypt it (it seems like encrypted is default)
resetting password of my original accounts from recovery mode 
changing the password to the login keychain in terminal in recovery mode in case my password on the keychain wasn't updated along with the reset password in recovery mode


I am running Mac OS High Sierra