Welcome to the Zoom Developer Forum – I am happy to help here. To start, please share the code snippet or screenshot of the request handling OAuth. This will help us identify what may be happening. You should also know we have a Postman Public workspace with done for you getting started API workflows. OAuth is on the requests you can reference and even generate a code sample in your preferred language. Here is a link to our Zoom Public Workspace.
Postman Public Workspace :
https://www.postman.com/zoom-developer/workspace/zoom-public-workspace/overview
Thank you for posting in the Zoom Developer Forum and sorry for the missed response.
Zoom API Authorization & Authentication Postman Public Workspace :
Let me know if this helps.