Connection to ONE particular website is limited.

I build and design websites with various hosting companies. I am having an issue connecting to just PART of this one company, Hostgator, on my computer.
I can connect to hostgator.com with no problem. I can connect to many of the links on the Hostgator site such as hostgator.com/domains or hostgator.com/chat. BUT, I cannot connect to Sign-In to my account. The link for that seems to switch to a subdomain, portal.hostgator.com. It times out.

I initially did all the usual stuff, rebooting, clearing cache, checking DNS. But then I noticed I couldn’t not access that one link on my phone too.

I talked to Hostgator and they say my IP was not blocked. My ISP came out and told me THEY do not block sites. But just in case, they gave me a new router.
What I discovered is NO device using wi-fi in my home could access portal.hostgator.com. I had 2 PCs, 2 Tablets and one Mobile phone and NONE of them could access portal.hostgator.
THEN, I discovered that if I use the cell signal on my phone, I COULD access portal.hostgator.com. If I turned my phone into a HOTSPOT all of these devices that couldn’t access portal.hostgator.com can now access it.

What is it about my wifi that I can’t access this one link? I even logged into the router itself and pinging the link didn’t work.

To sum, I have a new router AND new computer along with other devices that can’s access this one link using my wifi, but they ALL can access the link if they piggyback off of my phone hotspot cell signal.
Any ideas?

ERROR MESSAGE
This site can’t be reachedportal.hostgator.com took too long to respond.
Try:

Checking the connection
Checking the proxy and the firewall
Running Windows Network Diagnostics
ERR_CONNECTION_TIMED_OUT