Hi there, 405/415 usually means HS is rejecting the request.
Could it be “content-type” instead? I personally use the nodejs library mostly, and the headers are handled by it. However I see that yours is “contentType” and maybe Google Apps translates it incorrectly.
Also it could be the querystring params at the back of your endpoint. Usually just stops at …/objects/companies/{companyID} and I’m not sure if this would be the case.
Cheers
WL