I was having the same problem, when I saw this forum, with so many ppl with the same issue of me...
I am so happy to say, that I finaly can use my "Merchant Outbox"
I would like to thanks to Arielle Simondsen, I have did what you said... I moved the "Merchant Outbox" fold, to main inventory.
And now I finaly can use it. Thanks to all that take your time, to help us! ♥