Desktop can't find comcast sign-on page, but my phone - using the same cable system - can.

My desktop is connected to a router. My phone and tablet can reach Comcast home page, but my desktop computer says it can't find it. I've used both Chrome and Edge browsers, searched for both "comcast" and "xfinity." It finds the page briefly, then goes to the "oops" page. I can't get to my email.