Itch.io may experience rare downtimes, clear cache (Ctrl+R) to make sure the page is loaded properly. PSD was tested on SAI and GIMP, are you sure there is a single layer and not a group that can be unfolded?
Yeah, I'm an idiot, missed expanding the group in GIMP. Thanks. I still end up with an endless loading cycle on the web editor (in Firefox), though.