I never heard of anyone uploading a complete blender file to sketchfab before.
Granted I hardly use the site, but from what I remember people usually upload exported meshes (i.e. .FBX, .OBJ, etc.) files to it.
So if your trying to upload a model, try that instead.
If its a whole scene... then maybe someone more experienced in using the site can help.
I don't know, but I am having a problem with Sketchfab. now how to submit work?
You may want to try using the Addon: https://github.com/sketchfab/blender-plugin/releases
Is there some other way than Sketchfab to upload files for review. I have had problems with them before. Otherwise I'll just bag this lesson and go on to the next.
No don't bag it, you're going to want your badge icon and you're 100% course completion stat. There is no other way than Sketchfab I think, meaning there's other website that you can embed? I'm not sure. But you can try it, Sketchfab seems to like other formats and also if you save in 3x versions of Blender. If Sketchfab is miss behaving, then upload and image with a composite of the shark sculpture from many angles. Perhaps that could work as well.
It seems that the only way to submit is to use SketchFab. I have a turntable submission on YouTube but can not enter that URL in the supplied box. Why does the instructor insist on using SketchFab?
I also encountered an error uploading the blend file to Sketchfab.
Seems like uploading with FBX format has (mostly) worked.