shopify add to cart button not showing WP site when firewall is enabled (as in using work intranet)

[bcatkins]

At RADUNITS.COM - I use the shopify lite add to cart button and it works I would say 95% of the time. But I get a call every month (who knows how much more often this actually happens) of the site appearing as normal - but without the Add to cart buttons where they should be. You can see on the individual course pages where the buttons should be - and some have sent screenshots to me while trying to access the site and it looks normal except for the Add to cart button missing. I wonder how much business I'm losing because this happens periodically. Usually, the site works just fine. Can anyone help?