"Object reference not set to an instance of an object." when adding new Node with SNMPv3

I am trying to add a NPM node with SDK through PowerShell using SNMPv3 as the Polling Method.

I CAN add the node using ICMP, WMI or SNMPv2 as below:

$NewNodeProps = @{

IPAddress = $IpAddress;

Caption = $NodNam;

EngineID = 1;

ObjectSubType = "ICMP";   

}

$NewNodeUri = New-SwisObject $swis -EntityType "Orion.Nodes" -Properties $NewNodeProps

$NewNodeProps = @{

IPAddress = $IpAddress;

Caption = $NodNam;

EngineID = 1;

ObjectSubType = "WMI";   

}

$NewNodeUri = New-SwisObject $swis -EntityType "Orion.Nodes" -Properties $NewNodeProps

$NewNodeProps = @{

IPAddress = $IpAddress;

Caption = $NodNam;

EngineID = 1;

ObjectSubType = "SNMP";

SNMPVersion = 2;

Community = "public";   

}

$NewNodeUri = New-SwisObject $swis -EntityType "Orion.Nodes" -Properties $NewNodeProps

All above result in the node created with the proper Polling Method.

However when I try to create using Polling Method of SNMPv3, as in the following:

$NewNodeProps = @{

IPAddress = $IpAddress;

Caption = $NodNam;

EngineID = 1;

ObjectSubType = "SNMP";

SNMPVersion = 3;

SNMPV3Username = "someone";

SNMPV3PrivMethod = "None";

SNMPV3AuthMethod = "MD5";

SNMPV3AuthKey = "somepassword";

}

$NewNodeUri = New-SwisObject $swis -EntityType "Orion.Nodes" -Properties $NewNodeProps

The response is:

New-SwisObject : Object reference not set to an instance of an object.

At line:69 char:19

+     $NewNodeUri = New-SwisObject $swis -EntityType "Orion.Nodes" -Properties $Ne ...

+                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    + CategoryInfo          : InvalidOperation: (:) [New-SwisObject], FaultException`1

    + FullyQualifiedErrorId : SwisError,SwisPowerShell.NewSwisObject

Been researching for several hours now and cannot find the answer.

What am I missing?

Thanks in advance...

Mike