I run into this error sometime when the server update and could a simple fix that one one can do.
First you need to login to your WHM cpanel.
now on the top left side look for the search bar and type in host
Then click on Change hostname
Now see if in current hostname the hostname is right if so just click on change and it will fix itself .
If the hostname is wrong just simple change it to something you like remember it needs to randomname.hostname.com for example server.kingsley.com or cheese.kingsley.com. after you change it just simple click the change button and your done.