Public and private notification groups abide by different rules when it comes to adding and removing recipients.
What are notification groups for?
Simply put, a notification group is a collection of recipients. Recipients can be organized into one or more groups for easy targeting when sending out a mass notification.
Public Vs Private Groups
Public Groups are available for all users to see and add themselves. Portal Admins are not able to add recipients to public groups, these users must opt-in themselves.
Private Groups are only visible on the 911Cellular Portal to Admins. Admins are able to manage the list of recipients in private groups.