Thanks for your interest in the plugin! The 'View Full Website' and 'Back to the mobile site' links generated by either the widgets or the template functions will only display to the correct device. I.e. the 'View Full Website' is meant to be placed in your handheld theme and only handheld/tablet users will see this link. Similarly, the 'Back to the mobile site' link is meant to be placed in your active desktop theme, and will only be seen after a handheld user has clicked the 'View Full Website' link.
This behavior may seem restrictive at first. But, it's meant to allow you to control how your users view your website.
Lastly, in your footer.php the line 19 looks like a feature of the theme.. that is not the Device Theme Switcher (the plugin we're speaking about now). They are two completely different things and may not play well together. I would recommend using either the switcher functionality of your theme, or this plugin.. one or the other.