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Thanks, the documentation page I had called them post parameters, your reference called them form data. When I added them as form data it worked. I think this has tripped me up before with the API documentation.

Show me the exact post call you made and how you pass the body in a form data (not a json object)

Check this API reference.

Also, the documentation states grant_type should be a parameter, we tried it as a Query parameter, we also tried passing JSON in the POST body. Which should it be? I'm running Fiddler and I'm very sure of what I'm passing. Thanks.