Changing the Router Security Setting to connect WiFi on a Vizio TV

I have a Vizio TV that won't connect to my new Xfinity WiFi Router.  It used to connect with both my own personal router and my older Xfinity router.  Looking on line this is a common problem with a Vizio TV when using the Xfinity Arris brand TG862 router, which causes a conflict and won't connect.  The fix is to change the security setting to "WPA PSK TKIP " .  I've talked to 3 Comcast representatives and even exchanged the router and I'm not able to make the security settingchange.  When I log into the router as the admin, the edit screen with the drop down security settings is grayed out.  Does anyone know how to make a change that will allow me to edit the admin security settings? Help!!

Bob