Welcome to the RingCentral Community

I have created a JWT token for my ungraduated app. I am trying in Postman the POST method to obtain an access token using this process: https://developers.ringcentral.com/guide/authentication/jwt-flow

When I use the sandbox URI of https://platform.devtest.ringcentral.com/restapi/oauth/token

I get error OAU-336: "Audience claim value is not equal to token endpoint URL".

So I tried Production URI of https://platform.ringcentral.com/restapi/oauth/token

Which then gives me a different error OAU-165: "Sandbox client is not allowed".

I have triple checked and my credentials are alright, I am passing in all necessary authorizations and parameters. I must be using the wrong URI but haven't found any others to try.