Error uploading model

I’m testing a Sketchfab to Mozilla Spoke workflow. I textured an object with an image, exported as an fbx, then zipped up the file along with its image material (I’m on Mac, so I did right-click and compress to create zip.). In Sketchfab, I’m shown a 404 error when I drag in the zip. However, when I click “view model,” it shows my textured object correctly. I hit upload (public), and copy the models’ url to paste into Mozilla Spoke. It shows as “Error loading model” and my scene has a missing file icon in place of the model. I figure this is because Spoke only supports glb/glTF and the free Sketch account doesn’t offer glTF conversion. So I restart the process by exporting my object as a glb instead of fbx before zipping it up and uploading to Sketchfab. However, I end up with the same 404 error in Sketchfab and “error loading model” when I paste the Url into Spoke. I’m lost as to what I’m doing wrong. Does anyone have any idea of where the issue could be? To be fair, I’m unsure if the issue originated in Sketchfab or Spoke, but since I get a 404 error, I assume Sketchfab.

edit: Could this be because I didn’t bake? On a side note, do you always have to bake before uploading to Sketchfab?