SSHD config to permit Users to login via PUBKEY only

I have situation where I have two users in server.
Root and brandul.

I have edited sshd_config and disabled password authentication and directed Key file:
AuthorizedKeysFile /etc/ssh/authorized_keys

I can confirm that I can SSH into root without any problems.
However, if I want to SSH to brandul user, I receive the following error:
Permission denied (publickey)

How can I add SSH key for SSH user or edit config that I would be able to login to any user SSH using a key from AuthorizedKeysFile ?

This config used to work for me in CentOs Panel

check if both public and private key are correct and accounts are created too