Hi sezm !
It seems like that your site is using both the
www.sezphotography.com and the
sezphotography.com variant. Browsers don't know if the
www is a trusted domain as they don't treat it as the 'same domain'. So the request is getting blocked by the browser.
If you go to the Buttonizer settings, you'll find an option called
Allow sub domains, turn that on. Then it should work with subdomains.
Another way to fix it, is by making sure your website is only using the
www variant or the non-www variant. Then you keep it consistent for visitors and search engines.