Getting Next Available IP / IPv6 Issues

I'm working on further integrating my application with SolarWinds IPAM. I'm looking at the SWQL Studio and see that IPAM.SubnetManagement has verbs for "GetFirstAvailableIp" and "GetFirstAvailableIpv6".   I'm having issues with both as well as the "StartIpReservation" (mind you I installed the trial so should be on current (IPAM: 2023.3.0 )).


If I invoke this directly in SWQL Studio or with Postman / My App / whatever, I always get the return:
Not Found.

From my code this:

Nor this:
    "subnetAddress": "",
    "subnetCidr": 24
result in anything but "Not Found"


This method seems to be broken all together.  SWQL Studio presents no args and returns (Scripting results in the same):

- <Code>
- <Reason>
 <Text xml:lang="">IPAM.SubnetManagement.GetFirstAvailableIpv6 failed, check fault information. Verb IPAM.SubnetManagement.GetFirstAvailableIpv6: Cannot find method 'GetFirstAvailableIpv6</Text>
- <Detail>
- <InformationServiceFaultContract xmlns:i="" xmlns="">
 <Message>Verb IPAM.SubnetManagement.GetFirstAvailableIpv6: Cannot find method 'GetFirstAvailableIpv6</Message>
This is how we're currently getting "Next Available IPv4".  However, this method does not seem to support IPv6.  If you call this with an IPv6 address, it always returns "2600:1700:1bca:2a1f:1815:b180:5390:0 is not a valid IP Address":

    "subnetAddress": "2600:1700:1bca:2a1f:1815:b180:5390:0",
    "subnetCidr": 112,
    "reservationTimeInMinutes": 10

I'm open to suggestions, but this seems like faulty IPAM methods.