Connection times out on all devices on same wifi

Hello- I'm having an issue connecting to one particular site from all browsers and devises on the same wifi network. We recently had our modem upgraded from our internet provider and did not have this issue with the old modem. The error I receive on all browsers and devices is 'The Site Cannot Be Reached ERR_CONNECTION_TIMED_OUT' (chrome).
Anyone outside this wifi network can access the site fine and when I switch my iphone from wifi to data I can access the site.
I've pinged the site, cleared the dns cache, etc. and nothing has helped. I've spoken with my service provider who has referred it to second level support but I'm not holding out a lot of hope.
Has anyone seen this before? Its literally only one site, and its one that I need and use everyday for work so its crucial that I get this resolved quickly!