two laptops on wifi - the win8 laptop lost wifi

two laptops and suddeny one lost wifi (win8) ...have airport extreme connected to comcast modem (all comcast ok as far as I can tell). also have AX upstairs connected via cat5 to swtich. so cable modem/AE/switch/AX.... AX not working either no IP. and Win8 laptop not connected on wifi. right next to it is a win7 laptop with wifi working fine.