To clarify, when you say that you’re trying to use OAuth to join a meeting, are you referring to how participants join a Zoom meeting?
If so, I should clarify that the supported way to have participants join a Zoom Meeting is to provide them with the join_url returned by our Create Meeting API/GET Meeting API.
OAuth would be used to authenticate requests to our API to perform actions on behalf of a user, but logging them into a meeting would not be one of these supported methods.