This has been happening for about a month now, and it's been driving me nuts.
In Firefox 111.0.1 on my Win 7 desktop, whenever I try to add or edit an image in a listing, I can't save or upload that listing. The buttons refuse to work, and a quick Crtl+F5 reloads the page to where it was before adding/editing an image. I've tried clearing Firefox's cache, replicated the issue in Troubleshoot mode (ie, it's not any addons causing this), and deleting browser history.
Firefox recently updated, which seemed to take care of the problem for about a day, but after that, the problem reared its head again.
Meanwhile, a quick jaunt over to Edge allows me to upload an image with no problem, even if I save the listing (complete with an image) as a draft, then open it up in Firefox.
Right now, I've been having to fill out listings in Firefox, saving it as a draft, then opening it up in Edge to upload an image, and then saving.
