To trouble shoot that problem you need to use the web browser developer tools.
Look in the script console for any script errors
These steps should give clues to the problem ie either files are missing or the file permissions are bad so it fails to serve the file.
Note that if you really mean fckeditor and not CKeditor, we stopped shipping FCKeditor with mojoPortal, you should go to Site Settings page, make sure CKeditor is selected in the editor dropdown list and click the save button to make sure it is applied to the site settings.
FCKeditor is a legacy editor that is no longer maintained, CKeditor is the newer replacement from the same developers.
Hope that helps,