Using Cookies to remember selections C#

I'm trying to use cookies to remember my selections on a page refresh because the page displays videos in divs and after a while, the videos get "stuck" and you'd have to reload the page. However, all the videos aren't displayed at once, only 10 at a time can be selected/viewed. They also would like to just log in and the videos they last selected to re-display so they don't have to click each item in the checkboxlist to choose their videos. What I get is the error label displaying "Previous Selections Not Available" So, the cookie isn't saved on the button click??
Here is my code and my cookie info:
Design view
Example div that is hidden or shown depending on the selection in the checkboxlist
        <div id="sec_cam1" runat="server">             <div class="box one_third">< ...