error/quiz/subneterror

From MoodleDocs

General info

A quiz may be set up so it can only be accessed from certain computers. For example, some instructors require that certain quizzes be taken in a testing center under the supervision of a proctor.

What do I do?

This error message appears when you attempt to begin a quiz from a computer which is not on the approved list. Ask your instructor which computers are approved to take this quiz.