Typical newbie mistake. I’ve done my best to spread this knowledge all over the wiki:
https://wiki.fogproject.org/wiki/index.php?title=Ubuntu_16.04_Server#Settings

set a username, recommended name is YOUR first name, or “admin”. Do not use “fog”!

And
https://wiki.fogproject.org/wiki/index.php?title=Password_Central#Local_.22fog.22_user

Please do not use the local “fog” user account on the server to do back-end work. Create another account and use that.

It’s other places too. I don’t know what it’s about but I think the force compels the human soul to set the local account name as fog