I the 'edit' and 'sell' buttons were not appearing for the Wall Art Sets I was creating. But I just discovered the solution, and I'm adding it here just in case anyone was encountering the same problem. I had to enable a frame option for the design. That brought the buttons for editing and selling back. I'm glad that's figured out now.
I was a bit disappointed that I couldn't choose a non-framed option, since some 'cheaper-looking' art may benefit from not having frames, both aesthetically and cost-wise. BUT if I edit the listing after publishing, I can disable the frame! That is a decent workaround.
