SIP
420 Bad Extension
The server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the unknown extensions.
जब आप यह कोड देखें
When the request includes a Require header with SIP extensions that the server does not support.
कैसे ठीक करें
Check the Unsupported header in the response. Remove the unsupported extension from the Require header or make it optional via Supported.