Home network not working

Suddenly since yesterday evening I’m unable to use the internet on my phone, TV, and laptop. I get a pop up box on my phone that says “cannot identify server identity” for outlook.com and for Susi.Comcast.net. I have not changed anything that would cause this. When I try to browse the web, it says it cannot connect to a secure server. I tried to disconnect the modem and router, but didn’t work.