My Galaxy Note4 as well as another user's Note 4 phones would not ring when receiving a call that was diverted from the fixed line phone. It just displays a message "call diverted" and shows the calling party number. So, if phone was in the pocket, the call could not be responded to. Same thing happens with another brand of Android phone, Honor 6x BLN-L21, so it seems that it is a general Android OS bug. Non-Android phones, including Samsung Galaxy U600, iPhone and other "classic"GSM phones DO ring when they receive a diverted call.
I reported this issue to Samsung Support and hope they will contact Android OS for a solution. So, do not try to make any "factory data reset" trials to see if it would work, as you would lose all your account ID/passwords , as well as programmed Home Screen panels when trying to restore your phone backup from PC via Smart Switch (another BUG! )
Checked again today and now MY NOTE 4 RINGS AFTER RECEIVING DIVERTED/FORWARDED CALLS !
Maybe there was an automatic s/w update that made it work.
Will check later with other Android users/brands !