From @thomasyu888:
Perhaps, I think these are some of the scenarios where a evaluation queue would be unavailable:
User does not have permission to view the evaluation queues
The specified challenge doesn't have evaluation queues.
There are no "open" evaluation queues (you can set quotas on time durations on evaluation queues and have them automatically 'close' after some time)
From @thomasyu888: Perhaps, I think these are some of the scenarios where a evaluation queue would be unavailable: