412
SIP
412 Conditional Request Failed
The precondition given in the request was not met. Used with SIP event state publication (RFC 3903).
Cuándo verás este código
When a PUBLISH request includes an If-Match header with an entity tag that does not match the current state on the server.
Cómo solucionarlo
Refresh the entity tag by performing a new PUBLISH without If-Match, then use the returned SIP-ETag for subsequent updates.