'Page' checkbox in Screen Options missing

I am trying to create a custom single product page for my woocommerce site which requires me to create the page and then go into product edit and choose from the dropdown list from the page metabox which custom page I would like to link it to. Now my problem is that on a fresh copy of wordpress and my theme ‘adventure tours’ it is displayed both under screen options at the top of the page on the product edit page along with down the right hand side when checked. So on my current website when I look for it, it is missing entirely from the screen options. Can someone please help? cheers