Hi @taehunchoi,
Are you creating a meeting by sending a request to https://marketplace.zoom.us/docs/api-reference/zoom-api/meetings/meetingcreate?
If you are able to join a meeting in SDK, that means your SDK key & secret is working well. If you failed to create a meeting using Zoom API, then the issue might be related to the API key & secret or the JWT token. Are you able to use other RESTful API in https://marketplace.zoom.us/docs/api-reference/introduction? If not, then your API key & secret might have some issues.
Thanks!