If a user is shown an in-app survey and doesn't respond (ignores the survey), they will be presented with the survey the next time they are eligible, which depends on the sampling settings that are configured in your dashboard.
Users are re-evaluated for eligibility by our eligibility engine each time they are 'seen' inside your web or mobile application. This is typically on a re-load of the page or new screen where the InMoment code is installed.