1 missing folder

I have received a new PC and my Outlook has also been reinstalled. All folders, as well as inboxes and outboxes were successfully transferred, only one folder that is very important to me was not transferred or was lost. I don't know why, even when I check my emails directly on the server, this folder is missing. When I reactivate my old PC and open Outlook, I see my missing folder. What could be the reason for this, how can I find my missing folder again? Also, my settings under “View” - “Folder pane” are set to “normal” and not to “minimized”! I would appreciate some expert help.