@eppy you can try disconnecting the cable between your main deco and your ISP modem for a few seconds. This solved the DHCP guest network issue for me and others. Do make sure you have the reboot...

@Scuba_Diver @David-TP I had the same issue with the guest network and do also have the same firmware as you (1.9.0) @Slacker878 No, the 1.9.0 still has the guest network DHCP issue Quick workaround...