Stuck trying to authenticate

Hey, I want to authenticate with the API and have tried to follow the instructions but am getting an error.

I am trying this: https://docs.talkdesk.com/reference/authorization-code-basic-post as instructed by encoding my client ID and client secret but am still getting a weird error below.

{"error":"invalid_client","error_description":"Unauthorized grant type: authorization_code"}

I am copying the python code almost exactly as it is in the instructions. Please could I get a call with technical support on this? Thanks