Sorry, I didn't notice you mention that logging in to the console works fine.
I would recommend a check of the database, done with: cc-config database --repair
If that does not work, I suggest running: delete osconfig
This will reboot the appliance and bring you back to the bootstrap process of asking you to set a password for the admin user, asking for its IP addresses, DNS servers, etc. It does not delete any of your custom policies, mail, quarantine or settings other than the settings it is asking you to re-set.