SoapUI integration with TestRails

Attempting to integrate test results into TestRails.  

Here's the request: 

"POST https://xxx.com/index.php?/api/v2/add_result_for_case/:RXXX/:CXXXX HTTP/1.1"

Where:RXXX is the Run ID and CXXXX is the test case ID in TestRails

I keep getting the following error.

{"error":"External auth: Authenticated successfully, but no TestRail user was found for the given account."}

I am entering my credentials vai teh Auth tab using Basic Authentication type so I don't understand the error.

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