@Hope1983 From the fog.log:
25.11.2020 16:31 Middleware::Response Invalid security token
That means the tokens used to encrypt the connection are not ok anymore. This happens over time or when changing hostnames for example. Go to the FOG web UI -> edit the settings of the host you got this log file from and click the big orange button named “Reset Encryption Data”. If you want to do this for several hosts in one fo you can create a group, put them all in and then go to the group settings and click “Reset Encryption Data” there.
For the database you want to take a look at the credentials stored in /var/www/html/fog/lib/fog/config.class.php. Though I would imagine it’s user “root” with an empty password which was still used in FOG 1.5.5.