Hello, I have one Patton SN4120 registered on my 3CX v12. Lately i found that my outbound calls are failed (not all times). On Server Event Log i found that: Call or Registration to xxxxxxxx@(Ln.10001@PATTON_1) has failed. [ V4 Patton_IP:5060 UDP target domain=unspecified mFlowKey=808 ] replied: 503 Service Unavailable; from IPatton_IP:5060. Can anyone help me? What is the problem? Thanks!