I have experienced the same problem, besides, a username and a password didn’t appear when finishing the Storage Node installation.
What I did to get it working is to change the password in the Storage Node at the /opt/fog/.fogsettings as well as in the main FOG server at the WebUI -> Storage Management -> All Storage Nodes -> “Your-Storage-Node” -> Management Password, so that both match the local user’s password. I can’t say if it is the Storage Node’s or the main FOG server’s local user, as I have the same password in both machines.
I think it is the same solution as wpsd’s, but instead of changing the local user’s password to match the one at .fogsettings I have changed it in .fogsettings to match the local user’s password.