You might encounter WHM showing "UNKNOWN" at the top next to the cPanel version number when logging in, this can occur due to the RPM database being corrupted and you must run the commands below to correct restore the OS Information correctly.
From SSH run the following commands
This script will help correct most RPM Database issues.
And this will correct the "UNKNOWN" section at the top of WHM
You will need to restart cPanel to make sure the changes take effect and are viewable
Another common case that this issue can occur is when the RPM database is corrupted. This can lead to some other issues such as the nightly updates being unable to complete as well. To check and see if your RPM database needs repairing as well, please review this guide: