If you do not wish to use a proxy, VPN, Tor or similar avoidance of the
default routing which you have on your Internet connection then I think the
only people worth talking to about this problem are your Internet Connectivity
Provider.

Either they are filtering / blocking your access to the site, or else someone
upstream from them is doing so, and your contract is with your connectivity
provider, so talk to them if it isn't working correctly. They in turn have a
contract with their upstream provider, so they can take the problem further if
need be.

Antony.

--
https://tools.ietf.org/html/rfc6890 - providing 16 million IPv4 addresses for
talking to yourself.

Please reply to the list;
please *don't* CC me.