API Returns User does not exist - But Webhook Events Received for User

Endpoint:
https://api.zoom.us/v2/phone/users/{user’s email address}

We are trying to use this endpoint to get a user 's record with their Zoom account email address. We receive webhook events for this user’s Zoom account email address.

Error:
“code”:1001,“message”:"User does not exist: {user’s email address}, message: The remote server returned an error: (404) Not Found.

Authentication Method:
Server-To-Server OAUTH

This code has been tested on our internal Zoom account, however, when we use it for a customer implementation we get this error. The customer has verified the users have Zoom phone licenses applied.

Thank you,
George Schally
Developer
CDC Software