Note: The error code is the last 3 digits of the code you see in the error notification. For example, if you see the error notification Call failed (code: 2202404), the error code is 404.

If you are receiving Zoom Phone error 603: The peer is busy. Please try again later., this means that the other party might have declined your call or could not answer it, and there are no alternative routes like voicemail to route the call.