Valid Image source URLs for Summary Cards with Large Image


I have successfully got twitter cards displaying an image that is hosted on my CMS (i.e. the URL for the image is “https://www.mywebsite/assets/social/imagename.jpg” for example.)
However, I understand it should be possible to set the “” as the image on a twitter card.
So the meta data would look like this:
<meta name="twitter:image" content="*TwitterImageID*">

However, I did this and the summary card with large image doesn’t display properly in the validator - the image doesn’t appear (just a blank wrapper) and the card appears to be a small summary card with a small image.

As I understand it, this should be possible (using the twitter picture URL in the image source for a card) after all - it’s just an image storage location. I’ve tested the image URL by just entering in the browser and it works, so it’s the correct URL.

There were a few threads on this that had gone cold - and they didn’t tackle this specific question.