To provide context, Respondent is an online marketplace giving participants that match the employment background, demographics, and location requirements access to projects posted by researchers on the platform.
Respondent does not select or qualify participants for studies this is handled directly by researchers.
Qualification for a project can be based on many factors and, even if one is 100% qualified, it does not guarantee an invitation to participate. Each project has a unique set of needs and projects fill up quickly.
So, if you haven't been chosen, it doesn't mean you've done anything wrong. The best thing to do would be to continue to apply to participate only in surveys that are the best fit for your background/knowledge to increase your chances of being selected!
Another great way to earn incentives is to refer qualified participants to the platform or to open projects.