I have figured out my problem. In my testing, I was only specifying 'Authorization' in my header, and that has not been an issue with any other Meraki endpoint I was interacting with. When I added 'Content-type':'application/json', my function worked as desired.   But for anyone else's reference on creating "Client VPN" users, the "authorizations" parameter is in fact expecting "authorizedZone" with the format of "[your security appliance's name] - appliance" ... View more