I was looking at the message system having received a new message (sent Nov 3) to which I responded. Then I found a message from long ago that I could not tell if I responded to or not. I could only find the inbox, but not the outbox even though there’s a checkbox when you send the message about saving a copy to your outbox. Then I received a message that a new incoming message for me had arrived but for the life of me, I cannot find it. The message system that showed me a message that I received yesterday would not show me this message that it said I had just received. >:( 
Good day Knotme.
I have checked my message system and it is working as it should. So, I have sent a message to the site Admin on your behalf.
Hopefully the Admin will check on this and fix the challenge you are having.
Please let me know when and/or if you get some help.
I?m sorry you are having this challenge and that I, personally, are not able to fix this.
SS369
The new message (which I assume) was the one I was notified of, has since arrived. Still no luck finding my outbox… :-[
Please send me, via private message or email, a screen shot of your messages page so I can help you to solve this issue, as all is working correctly on the backend, and their are no blocks or holds on your account.
While taking screenshots for you, (re?)discovered the Sent Messages, so you can cross the Outbox thing off your list. Sorry!