Error .../Invoke/Orion.Nodes/ImportListResourcesResult

Hello everybody,

I am trying to get a node's resource list using the REST api with http calls. I can launch the job and check its status. But when making the request Invoke/Orion.Nodes/ImportListResourcesResult I'm always getting the error:

     One of the known types provided to the serializer via 'knownTypes' argument was invalid because it was null. All known types specified must be non-null values.

Probably because I am a bit new to Solarwinds I have no clue what the error is referring to.

What I do:

    1. Post a request to .../Invoke/Orion.Nodes/ScheduleListResources with body { "nodeId": 6 }. A job id is returned. For example "05fd1a93-e069-4a96-a3ad-d82e6affc4a4".
    2. Post requests to .../Invoke/Orion.Nodes/GetScheduledListResourcesStatus with body { "nodeId": 6 , jobId: "05fd1a93-e069-4a96-a3ad-d82e6affc4a4" } until the result is "ReadyForImport".
    3. Post a request to .../Invoke/Orion.Nodes/ImportListResourcesResult with body { "nodeId": 6 , jobId: "05fd1a93-e069-4a96-a3ad-d82e6affc4a4" }. This always returns the aforementioned error.

There seems to be a timeout for importing the resource list, but I am pretty certain I'm doing the import request within seconds once the status became ReadyForImport.

Am I missing something in the import request ? Or maybe Solarwinds is incorrectly configured ?

Many thanks for helping a struggling SW newbee ! :-)