The h-index does not depend on the impact factors of the journals in which you published. An h-index of 3 means that you have 3 papers with at least 3 citations. To increase the h-index by 1, you have to have 4 papers with at least 4 citations. You published several papers in 2024, and these will be cited in the course of next years. Please note also that very often the list of citations found by ResearchGate's automated algorithm is incomplete.
As mentioned, it often takes a long time to increase the H-index and the method I find best is to discuss the topic with people with similar research interests, who might cite my work in their future publications.
Your H-index may not increase if the new research hasn't yet received enough citations to impact it. The H-index reflects both the number of publications and the citations each publication receives, so it depends on the citation performance of your added work.
It is crucial to understand that the h-index measures both the productivity and citation impact of a researcher. Publishing in high-impact journals can increase visibility, but the h-index depends on the number of citations each article receives. Factors such as citation patterns specific to the field, publication time, collaborations, and self-citations influence the h-index. Therefore, to increase your h-index, it is essential not only to publish in high-impact journals but also to promote the citation of your work through collaborations, conference presentations, and academic network promotion.