Problems with importing a PST into office 365

Trying to move data from an inhouse exchange to office 365 in another domain (user is moving from company A to company B. he wants to take mail from company A into his company B email address).

In outlook, we exported his mail into a PST.  It's about 7.5GB - loads of folders under the inbox.

I set up an intermediate machine, connected outlook to company B office 365 and imported the PST into this account.  I see all the mail in this intermediate machine.

But on his company B machine, after days of syncing / after it saying all folders are up to date, there are loads of folders that don't have mail.  They aren't in OWA either.  So for some reason some folders contents didn't go from the intermediate machine to the office 365 machine.  Any advice on how to force it?  I see the contents in the company a machine, in the intermediate machine (populated by importing the PST), but on his machine, all the folders were created by syncing to office 365, but not populated (because the data isn't on the office 365 server either).

How do I force the intermediate machine to repush to the office 365 machine to send ALL the imported data into office 365?