Thank you for reaching out to the Zoom Developer Forum. The error message that you’re seeing is accurate. Currently, our User Level chat APIs require that you access them with a user level OAuth app or that you consider the following caveat when using an account level OAuth app:
One option would be to authorize the app manually once in order to obtain an access token and a refresh token. Then, prior to making your request, you can check if the access token is expired. If it is expired, you would then use the refresh token to refresh your access token. Finally, you would proceed with making the request.
In this fashion, you would only have to manually authorize the OAuth app once every 15 years as a refresh token is valid for 15 years. We plan to improve how OAuth works to make this process easier in the future.