Linux Mint FBCE version 19.3 not accepting password

I introduced Linux Mint to a friend to escape Microsoft and apple. Installed Mint 19.3 FBCE on his VivoBook. All works except when the system times out and then asks for a password and will not accept correct password at the login in box after waking system up. Have changed password and now won't accept new password or old one. Have to restart computer. Any help would be great.