App Preview

Hi there. I need to present my app in mobile view in a Webinar. I am having difficulty with the preview. There are 3 modes, Mobile, tablet and open tab. Previously I was able to open the mobile preview in a new tab and see it as it would be on a mobile on my PC. Now I don’t seem to be able to. And when I click on Open tab it previews an older version of the app.
Please help as I have to present on Monday.

You can open the mobile preview from My Apps page if you click the “Preview” instead of “Edit”.