How to get Mobile users to signup for a Web App

Hi, We have a web-based product live that helps users offer paid 1:1 consultations/ monthly chat subscriptions to their Audience. After analyzing our analytics data I found that we have a very low conversion rate on Mobile compared to Desktop. While the product has a responsive design, we are not sure what is causing the drop-off on mobile UI. Is this a common problem faced by a lot of companies/ products? We don't have a mobile app at this point, but we are working on one. Our Average Engagement Time on Desktop is 4:30 Mins, while the same for Mobile is 0:40 Mins Would really appreciate any form of help/guidance. Website Link: https://www.hiretheauthor.com/