This article helps explain why this happens and some tips and tricks for identifying where the link is. We'll try to cover the more common situations first and get more technical later.
The link is hidden in a navigation menu
While we try to do our best to show links in navigation menus, they sometimes are hidden too deep or there is a technical issue that prevents us from making these apparent.
The link only displays at a certain browser width
Many responsive sites contain the links for both mobile and the desktop versions. The mobile version is simply hidden until it detects the browser width at a mobile size. You can try to resize your browser window to see if the link appears.
The link was not intended for humans to click on and therefore is not visible
You may have some links in your source code that are not visible to humans, but are intended for search engines, robots and other technical purposes. Keep in mind that if our crawler is finding these links, search engines are also finding them.
Tips for finding the missing link
Switch the Page Report into "Show HTML" mode by clicking on the icon in the top of the Page Report. This will often show you where the link resides in the HTML, and reveal the link. Hopefully this gives you some insight into why this link is not visible on the live page. In some situations it may require your developers to explain why the link is not visible, or you can always submit a support ticket and we can review it with you.
If after switching to "Show HTML" the link is still not highlighting, try using the find feature (Ctrl+F) in your browser to locate the link. When searching for the link you may have more success performing a partial match on the link. For example, if trying to find "http://www.example.com/news/article/2015/02/news.html" perform a search for "news.html".