How we can improve our selling/promotion strategy?

We have launched ASO by 2Stable (https://aso.2stable.com/) more than 8 months ago, since that time, we have added a lot of new features and improved our project, however, we have 0 active subscribers. ASO by 2Stable is a tool that is oriented on a very targeted audience, specifically on iOS,macOS, and iPadOS developers. It's an App Store Optimization tool, that can be used in different ways, first one, for investigation & research and the second one, for monitoring and tracking. The developers can investigate the App Store by finding the most trending apps, in every category (Free, Paid, and Grossing) and also they can search which apps are ranked by a specific keyword. Now we are finishing the new features that will allow users to monitor and track their app's performance, in other words, they would be able to track and monitor category rankings for any app in the App Store and measure the impact of their metadata updates by monitoring the keywords history ranking. When we first launched our project we had a premium subscription of 9,99$/month, however, after 4 months we had 0 subscribers and we decide to make our project free, we hoped this will increase retention and downloads, but it hasn't. Now as we plan to release a new version that will allow users to monitor their app's keywords and ranking, we have some doubts about how we can monetize our project and at what price. Some of our competitors are limiting the number of keywords, some are limiting by countries. How would you monetize ASO by 2Stable and why?