VMware Aria Operations 8.18.x
This issue occurs because the Authentication Password and Privacy Password have not been entered, even though the Authentication Protocol or Privacy Protocol is configured in the Edit Outbound Instance configuration screen for the SNMP Trap Plugin instance.
Enter the Authentication Password and Privacy Password in the Edit Outbound Instance configuration screen, run the TEST, and verify that "Test connection successful." is displayed. Afterward, click SAVE to save settings.