RETURNED TO THE CALLEE. The call invitation received by the callee fails: the call invitation expires 60 seconds since it is sent, if the callee responds to the call invitation but neither the caller nor callee takes any further action ever since (cancel, accpet, or decline it).
RETURNED TO THE CALLEE. The call invitation received by the caller fails: the caller is offline.
RETURNED TO THE CALLEE. The call invitation received by callee fails: the acceptance of the call invitation fails.