You need the image link ending with the extension. So in your case the link i.imgur.com/C1IRWR0.jpeg. If you open your imgur.com/a/x2WYqTV link, right-click on the image and select ‘copy image link’ (or ‘open image in new tab’) to get the correct url).
@collect,do you have any idea as too where I could find an official source so If i end up sending more of the banpresto jumbo cards to BGS? I’m afraid if i send them to BGS with no info, they might return them, minus the one they already graded. thanks!