I have a simple solution. Close Outlook, Pause Syncing (2 hours is smallest increment), count to three, Un-Pause syncing.
Your Outlook file should upload.
Now, before you kick up and open Outlook on another computer (which I do), either logoff or shutdown the first computer. You DON'T want to have both computers logged on as there is a chance Outlook will load in the background and suddenly you will have two (2) versions of the PST file, although it will be uniquely named like "Outlook-MyComputer.pst" You will then need to figure out what is the latest Outlook file and then delete or rename the files. It is a bit of a pain.