This is a QuickBooks issue and is easy to resolve
1. Login to QuickBooks as an administrator in single user mode.
2. Click on Employees menu at the top, go to Enter time and select weekly timesheet.
3. On the weekly timesheet screen, from the Name drop down select the employee whose time you are trying to send to QuickBooks.
4. Go to Previous timesheet and then return to active timesheet page again.
5. Once this is done, go to TimeRewards and try to transfer the employee's timesheets to QuickBooks. It should work now.