"Please use an image that's at least 200x200px and is accessible from Facebook."

Figured it out no worries.

Hello tdocc,
I’m having the same problem, can you tell me how you’ve fixed it ?

Btw on my 2 different posts, I have an image with the same size, and on 1 of the posts works just fine on the other one it gives that message you mentioned in the title.

Facebook tends to have a delay when utilising a new featured image – so I think you need to wait at least 24-48 hours for it to be detected properly.

However instead of using 200×200 or similar, I rely on 300×300 or 400×400 images to be used but with a lot of white space around the image (which is small and in the center of the overall image file) so it isn’t stretched by Facebook. Takes some trial and error.