Cannot acces WordPress on WIFI

Cannot access my site or my provider’s site thru wifi. Have already reset the router & modem, purchased a new router, called the internet provider and the host platform HostGator and cannot find a solution.

The site can work through our phones on 3G or 4G, but not through our Cox internet provider. After purchasing a new router last week the site was visible for three days and now comes back with the error failed to open page.

Please help.

Thank you in advance.