SIP
580 Precondition Failure
The server is unable or unwilling to meet some of the preconditions specified in the request for resource reservation.
When You See This Code
When using QoS preconditions (RFC 3312) and the network cannot guarantee the required quality of service for the media session.
How to Fix
Relax the precondition requirements or ensure the network path supports the required QoS. Consider removing precondition requirements for best-effort calls.