Holysony,
There could be a lot of reasons why visitors are not converting. Here are some common ones that you could check against.
-Ambiguous or confusing conversion funnel (i.e. forms that are too long, forms that are confusing, check out processes that are confusing or poorly designed, buttons that are hard to see, text that is not descriptive enough, etc)
-Keywords not present or prominent on landing page
-conversion funnel functionality issues (i.e. elements don't render in some browsers, forms or other actions do not work or to not work under certain conditions).
-Ad keywords and value proposition not relevant to landing page
It sound like from your description that they are spending a lot of time there but not converting. Do you have too much information on the page? Is your action (whatever they are supposed to do) clear enough? Does it work in all browsers and under most conditions? Typically if people are spending time on the page but not converting, they are doing something and then deciding against converting for whatever reason. I would start there.
You could also experiment with different versions of the page. Try removing an element or two and see if that helps. Conversely, maybe there are elements that you need to add.
Maybe you can find an idea here,
http://www.adherecreative.com/blog/bid/120575/4-Mistakes-That-Kill-Landing-Page-Conversion-Rates
If you can post a link to your landing page I would be happy to look at it.
Best,
Shawn
