Ok. I've changed "the best possible translation" (this is how Duo calls it) to
The judge [is not waiting/does not wait/will not wait].
The solution with referee and steward has actually been suggested by several users of the course - so, that's why we included them as well.
Let me add that the sentence "A bíró nem vár." also lends itself to the interpretation "The judge is not a castle." (vár (noun) = castle). This is also accepted, albeit not as the best possible translation.
Thanks for your comment.
I knew it would not be accepted, so I answered the above. But my reading of this sentence was also: "The judge won't wait (for you, so hurry up)." The correct grammar would be something like "A biro nem fog varni (te rad)" but when expressions like this were used, it usually was meant as a reminder that authority figures won't wait for you and you'd better be punctual. And so it was shortened to the simpler expression "A biro nem var." (Implication is now "..for anyone" so it's less aggressive and personal.)