I have the same issue. I found this "you must contact Splunk to ensure that the credentials being used have access to the API on port 8089"
here:
https://interset.zendesk.com/hc/en-us/articles/115004545887-com-splunk-HttpException-HTTP-401-Login-failed-with-Splunk-Cloud
Please respond if you managed to get this working, I am struggling to get a response from Splunk (I cannot raise a request ticket).
... View more