Siemens HIPATH 8000 - Manual (Page 241)

Troubleshooting
241
SIP Server not responding
The SIP Server Address has been set but the SIP server is not responding
(Code 10).
Possible solution
Check SIP realm (Æ page 115).
SIP registration error
The SIP server/proxy has rejected registration of the phone (Code 11).
Possible solution
Check SIP user ID and password (Æ page 115).