The data is refreshing on the back end per the schedule you've set. It doesnt automatically update the report after you've viewed it. You need to automate the page refresh. So you need to use another mechanism to force the page you are showing to refresh on some schedule to see the up dated data that was updated on the backend.
Here are some techniques you could utilize on the page you are displaying the powerbi dashboard from so that it refreshes every 30 minutes
HTML approach
<meta http-equiv="refresh" content="1800; URL=http://www.yourdomain.com/yoursite.html">
JavaScript approach
setTimeout(function(){
window.location.reload(1);
}, 1800000);
powerbi-embedded
tag? Is this dashboard embedded in your app, or you are showing it from powerbi.com directly? – Andrey Nikolov