Featured Images not showing

Same for me. Event when the default image is set, no image shows on the actual AMP page. When I run it through Google’s structured data testing tool, it finds the image.

This has been resolved with the latest update. The team of Yoast delivered a new version of the plugin fixing some of the mentioned bugs.

Got the same problem. The latest update has not fixed the problem.
When using PageFrog is works

One month later, still no featured image…

This might help. Remember, featured images need to be uploaded at a size of at least 969px wide.

https://megamikejr.com/blog/mobile/add-amp-featured-image-wordpress/

the problem depends on a wrong json format like this
“width”:1400,”height”:513
json require the use of the “” for keys and values.
G.