My app is not in ranking in App Store for added keywords
App Store rankings for apps under various categories is based on algorithms employed in the Apple's servers. How the ranking process works is not public knowledge.

So, there is no definitive answer as to why your app is not there in the ranking (maybe there's a minimum threshold to compete for ranking).

Additionally, why or how Apple does something doesn't fall under the purview of what's discussed on this site. It is generally considered off-topic. Please have a look at these links:


http://meta.apple.stackexchange.com/questions/2508/why-were-not-customer-support-for-company-x-or-product-y
https://apple.stackexchange.com/help/on-topic
https://apple.stackexchange.com/help/dont-ask