Quickbooks invoice number sync issue

Sometimes I will create invoices in DF and sometimes I will create them in QB (not duplicates). I found an issue with the invoice auto-numbering between QB and DF. STEPS: I created an invoice in DesignFiles and an invoice number was automatically generated #17255. For some reason, this invoice did not sync to Quickbooks and the invoice was not showing in QB. I left it until I had time to contact you to figure out how to fix it. When I next created an invoice, for a different client, instead of entering it in DF, I created it in QB. However, QB numbered the new invoice #17255 The same invoice number that was used to create the invoice that did not sync to QB for the other client. This is creating a mismatch and may be causing sync errors. I then changed the QB invoice #17255 to a new number, thinking the DF invoice will now sync. That did not work.