SIP 403 is shown when the server understands your request, but is refusing to fulfill it. You will need to contact your VoIP service provider or PBX administrator for assistance.

The most common reasons for this error:

- The username and / or password are wrong;

- The server is requiring an authentication username and password and none have been provided;

- The user is not allowed to call the destination (or is using the wrong international dialing prefix), or there is insufficient account balance;

- The phone is trying to register too fast and the server has blocked the phone for that reason;

- You are trying to register multiple devices at once and the server is blocking the phone for that reason;

The exact meaning of the error message depends on the PBX configuration or the VoIP provider. The Zoiper team cannot provide you with the reason. Please contact your provider for further assistance if the suggestions above do not help.