Based on the description, it seems like you may be trying to Authorize a user from another account, is that accurate? If so, then in order to test your Zoom integrations with external Zoom accounts you would need to test with a Publishable URL. This is because Zoom restricts unpublished App access and use to internal members of the developer’s Zoom account. I’ve linked several support documents on this topic for your reference.
Sharing private apps
https://marketplace.zoom.us/docs/guides/publishing/sharing-private-apps/
Publishable URL FAQ
https://marketplace.zoom.us/docs/guides/publishing/app-submission/publishable-url-faq/
By publishing your app on the Marketplace, your product or service is introduced to millions of daily users looking to connect workflows and discover new tools. Once a user successfully goes through the OAuth flow, you will get an access token and a refresh token. You want to store the refresh token and use it to get another access token which can be used to make requests against Zoom API (i.e generate the meeting link.)
Publishing your app on the Marketplace exposes it to millions of daily users seeking to integrate workflows and explore new tools. After a user successfully completes the OAuth process, you will receive an access token and a refresh token. It is recommended to save the refresh token and use it to obtain another access token for making requests to the Zoom API (i.e generate the meeting link.) Here some helpful support documentation on this topic:
OAuth with Zoom: Refreshing an access token
https://marketplace.zoom.us/docs/guides/auth/oauth/#refreshing-an-access-token
Things to know before creating an app
https://marketplace.zoom.us/docs/guides/things-to-know/
Publishing an App
https://marketplace.zoom.us/docs/guides/publishing/
Please let me know if this help to clarify the behavior you are seeing.