ONTAP 9.10 is used. I am testing SNMP v3 Trap transmission, but I cannot receive it well on the SNMP Manager side.
For SNMP v2, I was able to confirm receipt of the Trap on the Manager side. I have the SNMP user and authentication settings on the Manager side set to match the ONTAP side settings, but I just can't get Trap reception with SNMP v3.
Packet capture showed that even though the Trap was sent with SNMP v3, it seemed to be recognized as a v2 Trap.
That being said, you may have already covered most of the steps. Generally we see these sorts of issues being related to network devices (firewall for example) sitting in-between the controllers and the receiving host.