When viewing the Invoices tab for a customer, there is a "Refresh" button next to the number of invoices. This button should initiate a re-sync to QuickBooks Online that imports newly created invoices since the last import, and updates the void status of any existing invoices.

I do know that inside of an existing invoice, there is a More->Refresh from Integration option, which is useful for being able to reflect the voided status of an existing invoice, but it's never particularly useful otherwise because 100% of our invoices are generated by Autotask and sync'd to QBO, and unless they are voided and recreated (and are thus a new invoice), they should never ever be changed in QBO and thus refreshing in FlexPoint is pointless.

However, syncing new invoices on-demand for a client would be useful since those voided invoices are likely replaced by a new invoice that needs to be sync'd (unfortuantely we're at the mercy of Autotask to QuickBooks Online sync to actually get them to QBO, but that's a known, if frustrating, quantity).