That means the resource that the program is trying to download has been moved, deleted or renamed. The 404 error is a web error indicates a resource wasn't found. This could happen because of many reasons, but in most of the cases because the program and the website/server where the updates were stored to be discontinued.
While that's not the case because the program still appears as being available, I recommend contacting the developers because this is a server side problem and only the developers have access and can investigate the issue.
Contact email address: