Is the fucking "cover" image file. I'm uploading a pdf product like I've done a bajillion times and once again the site won't go public on my product because no fucking cover image has been uploaded. The fuck it hasn't! Like twelve times. And once you get a cover image accepted try and change it. Another impossibility.
Also, I have never been able to delete a product once I have put it up. Anyone who has gone through this rodeo as much as me have insights I am down to hearing it. I have been putting pdf product up on their site since 2013 and I seem to get more and more lost every time I log in to add more stuff. It is a thumbnail graphic of the image. Why is it such a fuck show?
For the thumbnail not changing: make sure you exit the site, wait 10 mins just to be sure, and flush your browser's image cache. Worked for me.
As for not uploading ... no idea. You could always contact them, they are helpful :-)
Don't use Chrome or Safari. Forget IE/Edge or whatever infernal incarnation it is currently called. Clearing their caches are crazy difficult sometimes, even when you do it right. Using Firefox can help.
In all of them, turn off any sort of caching that is offered and pick the clear all data when the browser closes. (Doesn't always help with Chrome or Safari.)
The other option is to open the developer console (pop it into a separate window to make things easier). Then find the setting that tells it not to use any cache. That usually does the trick when I'm doing development. Sometimes iframes can still be an issue.