Troubleshoot a VideoBox type overlay plugin on a webpage

I have a page on my website which is essentially a copy of an existing source page on another site. It is a video gallery. On the source page videos open in a lightbox/videobox style overlay. On my page (which is not live yet) it opens as a separate YouTube page. Even if I copy and paste the existing working page into a new html page with all the links going to the original site it still does not work! I want the problem fixed or alternatively videobox or similar incorporated into the page to do the same thing, maintaining all the existing layout and functionality.