OK your add to site page is different to mine as when I click add to site the add to power store say add to power store 3 and the code is as below:
<input type="hidden" name="powergallery" id="1" theme="light" value="/var/www/vhosts/canopiesuk.com/httpdocs/gallery/galleries/ribbon_lightbox/index.php" />
see screen grab attached
Just too add I am using CMS V 1 not 2