The Pinterest search engine is based on a “Smart Feed” that ranks your content personally for you. This means that every individual has access to a unique and custom search feed based on their own interests, people they are following and past activity on Pinterest.
Additionally, newly added pins can take upto 3 months to show up on the search feed and that is heavily determined by the engagement rate on the pins. Keep in mind, that Pinterest is a user-driven search platform which means that even if your pins had a high engagement but another creator’s pin is going to serve a better experience to the particular user, then they will likely see a different pin on their search feed.
To learn more about how the smart feed works, you can check out the Pinterest Engineering blog article here.