Follow these 5 steps carefully and fix issue in your whm server.
Step 1. Login Your WHM as root.
Step 2. Navigate to Home & go to >> Server Configuration.
Step 4. Click on the button ‘Domains’.
Step 5. Search the option ‘Allow Remote Domains’ and Enable it on.
Step 6. After enable it then click on save button.
Hence, after you click on save button then setting will be changes. In this way you can fix this issue in your server. If you not understand then follow my image tutorials Click here