When cu has error to discover snmp v3 devce in nnmi,  one thing we need to check if cu has put in right snmp v3 username/password/Authentication/Encryption method-password etc in nnmi.

A good/fast way to make sure cu put in the right parameter is to use third party tool SNMPTester  to  test first. If third party tool SNMPTester can NOT connect, that means cu provide the wrong parameters.


Ask customer to install third party tool SNMPTester on nnmi server. Check if they can use third party tool SNMPTester to connect node(The sample Node IP : <IP>) with V3 user and password.
If still failed with use third party tool SNMPTester, this points out the issue is in device end.
https://www.paessler.com/tools/snmptester