Unfortunately, no refund can be given in such a case. There could be several factors contributing to the lack of ranking, such as lower sales compared to competitors, not utilizing PPC, seasonal fluctuations, issues with your listing, insufficient use of Rank Juice, a product price higher than competitors, de-indexing, losing the buy-box, deactivated listing, and new competitors entering the market. It is advisable to optimize your listing prior to attempting to rank.
If you are unsure, you have the option to purchase per keyword ranking for $500 (limited availability) or subscribe to the lowest monthly tier, Tier 1.