We're currently having trouble with our mobile landing page. For some reason the link opens the desktop version when a user clicks it on his or her phone, causing it to have a horizontal scroll bar (because the landing page is wider than the screen). Our designer used a free form template and it says it is mobile compatible. Any ideas how to troubleshoot?
The fact that the free-form template is Mobile Compatible, doesn't mean it will automatically look good on mobile. You need to active the mobile version of the page and style it the way you want it to look from within the free-form landing page editor.
See this doc for more information:
Why not you should go with Guided Responsive template? You will have more flexibility their. You can create responsive design easily using bootstrap or if you already have the responsive code the just put the code in a guided template and try it out.
If you do not want to go with this option then activate the mobile view on your free-form template as Justin suggested.