Problem mit gigaset N670 und Placetel SIP Verbindung

[NoobPhone]

We use the gigaset n670 IP pro base station to connect our S650H pro handset to the Placetel via a SIP connection. However, the SIP connection is rejected and when logging in to the web for gigaset, the SIP connection also looks interrupted. I have attached images for the mock setting of one of the devices. Could someone help me by pointing out a possible problem?