When you click on 'Upload', we send your Listing to the Portals. If there's an immediate issue with the file, you'll usually see an error pop up below the Portal Settings (as per the below screenshot) and you'll see a Red dot next to the Portal that it failed to upload to.
Click on 'see error log' to view further details of the error. The error log will also let you know if it's best to contact Rex Software Support or to go directly to the Portal to have the problem fixed.
Sometimes you'll see no error, but your Listing still doesn't appear on the Portals. This is because the Portals have accepted the file we've sent them, but when they've processed it, they've found an issue.
Unfortunately, we can't show this error in Rex, as the portal doesn't send us any information on the issue they've found. In cases like these, it's best to contact the particular Portal's support team for further information and to have the problem fixed.