Quickbooks Online Conversion

For the Account Numbers I believe you need to go to:

Settings > Account & Settings >Advanced >Edit in the Chart of Accts > Turn ON Enable Account Numbers.

As for the Balances, this is the ending balance in the Register or what's show on a Report?  Sometimes the Reports will grab periods and exclude transactions.  And when you say you "upgraded our Quickbooks online over the weekend..."  Do you mean you converted over your QuickBooks Desktop to Online?  If so you can start over again and redo the Import.

To do this, log into your QB Online Acct and then you want to delete everything after the  ".../app/" in the URL. (e.g.  https://...qbo.intuit.com/app/[DELETE ME])  Then add "purgecompany" to the end and hit Enter and say Yes.  (e.g. https://...qbo.intuit.com/app/purgecompany)

@LisaEdmonds 

Did you upgrade your QBO plan or else? Try opening your QBO account on any private/incognito browser to make sure.