Sync Error: Invoice #I128 is locked by QuickBooks

HOW TO FIX THIS ERROR MESSAGE.

Here is how you can view your sync errors: View Sync Log

How to view error messages on the Manage Account Website:
-From the Manage Account Website, click on Reports.
-Click Sync Reports.
-Click Sync Log.
-The top section shows the syncs you have run. Click on the most recent date.
-The bottom section shows the details of the sync. Errors are in red and notices are in green, so it's easy to -scroll through and see what the errors are.

SYNC ERROR: An error occurred updating invoice I128. Details: Invoice #I128 is locked by QuickBooks, so the sync cannot update it. If you or someone else in your office is editing Invoice #I128, please close the edit window and run the sync again. If no one is editing Invoice #I16128, then close your QuickBooks and reopen it, then run the sync again.

When you edit an invoice, QuickBooks puts a lock on it, so no one else can edit it.
When you finish editing an invoice, QuickBooks is supposed to release its lock, but it doesn't always.
The first step to resolve this is to close and then re-open QuickBooks.
If that does not work, then reboot the computer your QuickBooks is on -- this always releases a lock.