Cannot visit my own website on Cox wifi

I own a website (www.byclue.com) which promotes nutritional knowledge and products. It is hosted by SiteGround. Right after Thanksgiving, I can no longer open the webpage on my home Cox wifi (I can visit other website like google, Yahoo, etc). I tried all devices (PC, iPhone) and none of them worked. The other Cox users in my area cannot open it either. However, if I switch to other ISP (AT&T, Comcast), I can open it with no problem. 

I contacted Cox customer service multiple times this week through Chat and phone. Since it is not a Connectivity issue, they blame it to my hosting company. My hosting company double and triple checked everything in their end and see no issues. I asked Cox to have a senior technical person to talk to me, or at least create a ticket , or do some test to help me diagnosis the underlying reason, but Cox refused to do so. As a loyal customer for about 10 years, needless to say, I am extremely disappointed. 

Today, after some research, I found a way to get around this problem in my home wifi: changing the DNS to google public 8.8.8.8. Once I changed it on my PC and iPhone, I can open the webpage! Unfortunately, other Cox subscribers still cannot open it, which is a big problem for my business.

Why this problem is not happening with other ISP? Is Cox hiding something? How to resolve this issue permanently?