My guess is that if they take down the public hosting, most clients would lose access to work they paid for and fiverr has no way to put these back behind an authorisation. It is just a public list of files, either everyone has access to your file, or do not, including you.

But it seems like they might've just pulled the plug for everyone. I cannot access images from a seller. They throw a 404 as well.

My guess is that there is literally no one there who knows how to fix this. Seriously, look through the proposed solutions here, plenty of devs wouldn't know how to do any of them. It might not even be possible, with their architecture, to fix it quickly and retain functionality. I have worked in a place full of noobs where I'm certain none of the devs including me would have the first idea how to fix something like this.