I have tried this on a landing page created from our own template, but also with one from the Standard Marketo Template for landing pages.
I go through the process of creating a new landing page from the chosen template and the click Edit Draft. I then see my Desktop landing page and click the Mobile tab. It says, "Mobile Version - Automatically activate a mobile version of your landing page" with an Activate button which I click.
It shows "Activating mobile version" for a few seconds and for a split second I have seen the the layout from the desktop version displayed in the mobile version, but then it goes completely blank - the page is completely empty yet the desktop version has a header, logo, footer etc as designed in the template.
As I say, this isn't just happening with our own template, it is happening with Marketo's own sample template too.
Thanks in advance,