One problem could be over fertilizing using too much Nitrogen. This will cause excessive lush foliage growth and either small or too little fruit set. Cantalopes having lots of flowers and no fruit could be an insufficient pollination problem. Bees are needed to pollinate the flowers that will eventually produce the fruit. Lack of bee pollinators or low bee activity due to cool weather or heavy use of insecticides could be the culprit.
Cooperative extension suggests hand pollinating using an artists paintbrush.
Hope this helped. I have a rabbit foot fern that has out grown it's hanging pot. Thanks for any tips. Enclose the pot in plastic until roots form and new growth begins. I have a large yard which borders a forested area and we have serious problems with deer this year more then any other year.