Website being blocked by Advanced Security

For the past several months our website has been blocked by Xfinity Advanced Security. An Xfinity user with this feature turned on who tries to access our website sees a "Malware and Phishing" page, or a "This site can't be reached" error, depending on their web browser. Users who are not using Xfinity are able to access our website with no issues.

The website in question is www.northern-goods.com

I have submitted the unblock request form found at https://spa.xfinity.com/report several times. I am certain that the form has been submitted correctly. Still, our website remains blocked.
I have verified that the website is configured correctly. There is no misconfiguration, and, as previously stated, users who are not using Xfinity have no issues accessing our website.
I understand that the Advanced Security feature can be disabled on a user's router. This is not an acceptable fix for this issue, as we are not able to control the configurations of our customers' networks.

Please whitelist this website, remove it from the Advanced Security blacklist, or otherwise resolve this false "Malware and Phishing" error that is blocking customers from accessing our website.

Thank you.