cannot access previously accessible website dns error

We are having a problem on our domain accessing a website we normally had access to. Our network has several sites and each of our sites has a domain controller and dns server. We have one main fsmo server at our corporate office.

When I am not connected to our network (using aircard or home connection) I can easily get to https://intranet.artizan.com    As soon as I am on our domain or connected to VPN (that our ISP hosts) I am unable to connect. I should note that when users connect to vpn it is set to static our fsmo server's IP address so users can access network shares, etc.
I spoke to our ISP and we did tracert tests to 204.155.61.221 it went through all of our ISP's routers and then hung up right before getting to to their site. The next thing I did was to hook my computer up to our network and then I staticed our dns settings to google's dns (8.8.8.8 and 8.8.4.4) so I could bypass our dns server.....when I did a ping to intranet.artizan.com it resolved the IP (204.155.61.221) but I still got a reply timed out.
anything that I can do to make this work like it used to? I can see this maybe being an issue on the server that we're trying to get to..perhaps it doesn't like the public IP we use to connect to it? Strange that we were able to reach this website just fine and then all of a sudden we can't.

Any suggestions would be fantastic. Thanks! I'm not an expert on root hints, conditional forwarders, etc. so any help is much appreciated!