Interviewer ask me question: My EC2 instance was running well till last night, but today morning its showing error “connection refused” or “ssh connection timed out” or “port 22 connection error” , what are the reasons of this error ?

i told him 1) in security group check port 22. 2) 2/2 connection 3) if auto scalling or load balancer then check target health 4) public ip change

but he said , there are other reasons , what are the other possible reasons ?