When the organizer sets up the category, they make advertisements for all of the designers who are participating. These advertisements have a starting state called “Created”.
When you drop a texture into the Dropbox in Second Life, the texture can ONLY be associated with an advertisement that has the “Created” status. If the advertisement exists for you, the dropbox will use that advertisement and set it’s status to Accepted, which means the advertisement cannot be reused by the dropbox.
If you are trying to edit your advertisement, you need to use the website to edit the texture. To use the website, click the “Marvelous Mania – Login Kiosk” object at the event, to get a link. The link connects you directly to the editor without usernames or passwords to remember.