Hi,
I ran into a bug that spine can't load the images for a PNG export when I have a specific skin selected and an open preview tab in the export tab. (there's a picture of what I mean)
I never had this problem with projects without any skins.
As mentioned above, I "fixed" my problem by closing the preview tab, but it took me some hours to find that out so I think it's a bug worth reporting.
Weirdly enough, when I export all skins and animations at once, only the first animation with the first skin will have these green "loading" images. The other ones will be fine.
I hope that I could help someone and in these times:
Stay healthy! π