This error can be caused due to a lack of access.  Check the following:
  • Confirm the API Username is correct.
  • Confirm the API Password is correct.
  • API user has the correct permissions for the call you are making.  
  • Confirm no group overrides are included on the API permission type.
If you need more information on creating an API admin record: How do I create a username and password that can log API calls in Luminate Online?