Either a router or channel issue. What channel is that router on?
As a test do these things connect to free hotspots? If so, it's Comcast's issue to solve.
I have Comcast Cable internet and a Motorola Surfboard sbg6850 Modem/Router combo , I can connect to it wirelessly from both my iPad mini's and both mine and my wife's iPhone 6's but my wife's laptop which I just installed Windows 10 on about 6 weeks ago, won't connect.I'm also connected on my Windows 10 desktop via Ethernet. I've tried resetting the modem/router to factory settings , changing the SSID name and shortening the password because I had a longer name and password (thought it might need to be shorter) I went from 2.8mhz to 5mhz and back , I uninstalled and reinstalled the drivers on the laptop multiple times. I can see other peoples networks but not my own. Also the router signal seems weaker than it was a few months ago when I got the modem/router , sometimes I only have 1-2 wifi bar's in the same room , in my bedroom sometimes none and our house is only 1200 square feet. I had DSL before and had that modem and router for years without many problems. It's frustrating but I'm not sure why some devices will connect and others won't. Any help would be greatly appreciated. I assumed the iPhone 4 is just getting old and even though the laptop is about 4 years old , it was running Windows 7 before I upgraded to W10 , I would think the laptop would connect no problem