So it appears there are no technical issues, and none related to the payment threshold. It is just that you are not getting any earnings from the content you are contributing. This indicates that you should submit better content that would fetch traffic and subsequently earnings.
I suggest that you start contributing to schools and college sections right away. Use the search box first (both the main one and the one in the respective sections) and if the institute is not in the section, then submit it. Secondly, try to write articles on admissions to premier universities and colleges and provide good-length content. Articles related to careers can also fetch earnings, such as 'Career opportunities after XYZ course' or 'Career opportunities after graduating in XYZ' or 'What to do after XYZ course' or 'Top colleges for (xyz course) in (city) or (state)'. Basically, you need to expand the range of topics that you write on. You can even refer to our AE section to get an idea of what type of information students are looking for to study further and what professionals are looking for to enhance their careers. As a reference, you can check the articles submitted by Soundharya. They are very informative and get reasonably good page views.
You can also use your StatCounter account to track which ISC pages are fetching traffic for you. It gives a general idea of the topics to write on.
If you wish to share any screenshots of your AdSense pages, you could send them to my gmail of iscmanagingeditor. I will check it out and give you input, and we can continue our communications directly on this issue.
When you make a commitment, you create hope. When you keep a commitment you create trust! ~ John C. Maxwell