Welcome to your interview.
The question is on your right: Diagnosing Port Mapping Issues. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
What do you do when port mapping is done but the project still does not work on other PCs?