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.