NTM SNMPv3 not working

What scan are you referring to?

Are you using Orion Maps? 

My understanding for Orion Maps is that its leveraging the NPM scanned data. So it shouldn't be scanning it separately from NPM. There is a setting on how often you want Orion to calculate the topology using NPM data which I believe is 2 hours by default. A manual initiation of this calculation can also be done from manage nodes -> more actions -> update topology; however, I don't think this causes any scans but is a calculation of already collected data.

Perhaps the issue you are having is that your SNMP credentials are working in NPM partially. For example maybe it is able to poll some OIDs but not the OIDs related to the NPM data which is used for Orion Map calculation. https://support.solarwinds.com/SuccessCenter/s/article/What-object-IDs-OIDs-does-the-Orion-Platform-poll-for-network-topology-information?language=en_US

You could try in the Solarwinds SNMP viewer or other SNMP tool to poll these OIDs related to mapping with both SNMPv2 and SNMPv3. If you find a difference it maybe an issue with the access given to the SNMPv3 user account on the device.

I just posted this to another thread. This SNMP v3 configuration works great on my Cisco devices:

snmp-server group <SOME-SNMP-GROUP> v3 priv read <SOME-VIEW-NAME> access <SOME-NETWORKS>
snmp-server user <SOME-SNMP-USER> <SOME-SNMP-GROUP> v3 auth sha <auth-password> priv aes 256 <priv-password>
nnmp-server view <SOME-VIEW-NAME> iso included
!
ip access-list extended <SOME-NETWORKS>
remark *** Add some networks ***
permit ip 192.168.1.0 0.0.0.255 any