API-generated images can't be dropped on ComfyUI

While I'm creating the workflow that I will be driving using a Python app, I can drag those images back onto ComfyUI to load the workflow. However, the images that are being generated by the API do nothing when I drop them onto ComfyUI. If I drop those same API-generated images onto pngchunk.com it shows the workflow just fine, so I know the JSON has been attached to the image.