First check if the ports for record and audio are released. If so, release port 5060 UDP for record and ports of the RTP range, bearing in mind that you must redirect the IP of your network to the IP of CIP 850.
Check in your terminal the Server, User and Password data.
Server: IP address or domain which corresponds to the IP of CIP 850. User: Name of the IP extension line created in the switch.
Password: SIP password configured during the creation of the IP extension line.
Check if the record port configured in your terminal is the same port as the one used for records by CIP 850 in Configurations > SIP > Bind Port.
Configure your public IP or domain in "External Address" of your CIP 850 in Configurations > SIP.
Configure the range of IPs of your local network in "Local network 1" in Configurations > SIP. The switch accepts syntax 192.168.0.0/24 or 192.168.0.0/255.255.255.0. Configure this field in accordance with your local network.