1) Have someone proofread your content for grammatical errors.
2) Be sure you aren't quoting so many other sources that hubpages thinks you've plagarized or that it's "spammy" for having too many links.
3) Make a list of questions people might have on your subject and make sure your article does a better job of answering those questions than the top google hits on your keyword.
4) Make sure the flow of your hub is logical. (Should you reorder your capsules?)
5) Make sure your article has the keyword in the title
6) Make sure each image is from a reliable source and of good quality, source credit is properly given, and each photo capsule has a title and a caption. Bonus points if you can put your keyword into the titles and captions.
7) Be sure you put your hub into the best category possible.
If you check through those 7 things you should fix the problem. If you want to email me the text and print screens of the hub I'd be happy to give you more specific feedback.