Contextly uses meta-data to know when a story has been updated.
If you update the image in your post, Contextly should pick this up.
However, if you are using Featured Images in WordPress, and you update the image, WordPress does not change the update time. This is a known WordPress issue.
1) Update your featured image.
2) Add a space and then remove it from the body of your post.
3) Press update.
If the image doesn't change in 10 minutes, drop us a note at email@example.com.