If after exporting orders into MYOB you cannot find them in the Sales Register but the Integration Application shows them as successfully exported then the first thing you can do is check your current version of MYOB AccountRight you are using.
Version v19.7 of MYOB AccountRight Plus, Premier and Enterprise comes with an error in the ODBC Driver which does not allow any error to be detected during an ODBC import. This means the ODBC driver will advise that an import has been successful even if an error is encountered.
If you upgraded to this version of MYOB then you will need to install an ODBC Driver Update from the following Web site:
http://myobaustralia.custhelp.com/app/answers/detail/a_id/34491/
Once you install this patch try exporting the order again and now the Integration should correctly display an error message explaining why that invoices cannot be exported.
If you are not using version 19.7 of MYOB then submit a ticket by clicking the "New Ticket" above or report it to us by email to support@innoventsoftware.com.au.