I was able to get this feature to work only after I made a dummy entry into the "Call Block" list. Without that it would not work. With First Ring OFF and using Nomorobo you will get NO rings for robo calls. (Normally Nomorobo blocked calls will generate 1 ring.) Not having any rings for robo calls is great! Panasonic should fix this bug or at least update the manual with this workaround.