I can reach it fine from my end here in Northern N.J. Perhaps posting the output of a traceroute to the site may reveal a clue.
Seems it's being blocked by Advanced Security, on the page it does give the option to proceed with caution.
Since there doesn't appear to be a way of "whitelisting" sites where you think the Advanced Security may be producing false positives or is being over cautious. The only option would be to disable Advanced Security in the xFi app or web portal.
(looking at the report in Advanced Security, says the site is classified as Phishing/other).
If it is, a trace will show that too.
Disabling Advanced Security allows access to the site for me anyway, just tested it. Obviously some content on there it regards as suspicious.