C7000 AC 1900 wifi won't provide internet

Using modem/router combo with Comcast blast Internet, starting last wednesday my wifi keeps disconnecting and when it connects it does not allow Internet access from the wireless devices, though it works perfectly using a wired connection. I called Comcast and they verified my service was fine and they could see my modem connected. I have done factory resets three times and tried every combo of settings I could think of. Problem persists. Any suggestions?