If there is no script installed in the root (i.e. public_html etc.) for your domain name but you still get the message stating that you cannot install more than one script in the root directory of a domain, it means that a previously installed script was not properly removed. To resolve this problem you should follow these steps:
1. Log in cPanel and go to File Manager
2. Navigate to .fantasticodata in your Home Directory
3. Delete the file installed_in_root.php
Make sure that show hidden files/folders is enabled in your file manager.