After selecting the notification rules and clicking on save it is no longer added.
Steps:
In the Activity Notifications -> Notification -> select any notification ex: Initial/Update Status for Requests/Incidents/Problems no default notification rule is listed, its blank. When we add any rule and save, it says successful but not added.
Release : 17.3
Component : SDM - Other
The issue was due wrong values in the table usp_lrel_ntfr_macrol_att_ntfrl. After identifying and removing those rows it is working as expected.