if you add a user to a group, you have to configure the read-view, write-view or notify-view for the group. Or NMS will have no authority (writing, reading, being notified ) operated on the user.
A user can be added to a group
set protocols snmp v3 usm-user <text1> group <text2>
delete protocols snmp v3 usm-user <text1> group
•<text1> the name of the user
•<text2> the name of the group
•This example adds user1 to group1