Mozilla, Google, and Apple are all blocking WoSign/StartCom SSL certificates. In January, Firefox 51 and Google Chrome 56 will release and, since the Project Argo site forces itself to use HTTPS, nobody will be able to access it anymore. For people on the beta channels for the browsers, this change is already in place: I am unable to go to the Project Argo website on Firefox Beta. You may want to consider switching your certificate to one that isn't blocked.
https://blog.mozilla.org/security/2016/10/24/distrusting-new-wosign-and-startcom-certificates/
https://security.googleblog.com/2016/10/distrusting-wosign-and-startcom.html
https://support.apple.com/en-us/HT204132