Fortiauthenticator 400C post upgrade problem

Hello everyone,

Colleague of mine upgraded our FAC 400C directly from version 3.x (I'm not really sure what the original version was) to version 4.1.2. FAC was not in use prior the upgrade and contained only baisc configuration allowing our management access (IP on port1, some user accounts). Our intention was to start using it after the upgrade, however GUI is inaccessible after the upgrade and error message pops up when using HTTPs. HTTP is not working at all. We are able to access using ssh, but there's not much you can do in CLI. I have already tried factory reset from CLI, but it didn't help either.

IP address used on the unit is 192.168.1.99 and is NATed to 198.18.61.5. I don't have direct physical access to the unit and therefore can't try HTTPs access from PC located in the subnet 192.168.1.0/24. I will probably be able to physically access the unit during the weekend, but I would still like to know, if there's something I can try before I have the access.

Has anyone even encountered described issue?

Thank you

Lubos