Facebook’s mobile app (m.facebook.com) does not support page tabs without explicit mobile app setups, therefore attempting to open your app URL directly may result in a page not found error due to a bug in Facebook (view report 1 and report 2)
The following trick can be used to view the tab on a mobile device when you need to show it to someone or do admin functions:
Where pagename is your page name from the original URL, and APPID is your APP ID
Page tabs are not designed for use on mobile screens, which may drive their exclusion from Facebook’s mobile app. The tab is a fixed 880pixels wide, even if you set the iframe to fluid. As a result, tabs will only look good when viewed on tablets or devices capable of scaling down the page to fit the screen. This is unfortunately not something we can solve with the plugin – your Social-Commerce formatted pages are all responsive and will adapt to mobile screens if viewed outside of the Facebook tab.
If you have a specific need to enable mobile for your shop, you must do so with a custom Facebook app.
For details , please visit your Facebook Developers tab and browse the discussions on this topic.