After you have synced to QuickBooks you can view the results on the QuickBooks Sync page.
If all records were synced without any issues the table will show zero unsynced records.
If there are any errors returned by QuickBooks you will see records that are still unsynced. Click on the "View" icon at the right of the row that has unsynced results to view the error message returned by QuickBooks.
Based on the error message you can try to correct the problem with the record. If you don't understand the error message or need help correcting an issue, just open a support ticket for more help. Records that have not been synced before will show a status of "New" and it will show as "Changed" if the customer record has been changed since the last time it was synced.
Viewing Sync Log
You can also view a log for all records that have been synced to QuickBooks by clicking the "Sync Request Log" in the sidebar of the QuickBooks Sync page.