SIP
408 Request Timeout
The server could not produce a response within a suitable time. The client may repeat the request without modifications at any later time.
When You See This Code
When the callee does not respond within the configured timeout (e.g., phone rings but is never answered, or the endpoint is unreachable).
How to Fix
Check if the callee's device is powered on and registered. Verify network connectivity. Consider adjusting the server's transaction timeout value.