The SNMPTD probe requires a unique Engine ID for each SNMPv3 device that is sending traps to the probe. The EngineID in SNMPv3 traps are necessary to identify unique network devices. A wildard engineid cannot be used and is per SNMP standard.
See the following link for more information on SNMP standards; https://tools.ietf.org/html/rfc5343
“To retrieve or manipulate management information using the third version of the Simple Network Management Protocol (SNMPv3) [RFC3410],it is necessary to know the identifier of the remote SNMP protocol engine, the so-called snmpEngineID”
See following statement in the SNMPTD documentation:
“User: This tab applies to SNMP v3 only. If there is a SNMPv3 trap, the message is rejected unless the SNMPv3 user sending the trap is defined. You can refer the user using a combination of the name of the user and an identifier for the given SNMP application that you are talking to (called an "EngineID").”