"There was an error when saving a Employees list, element "Employee_Name". Quickbooks error message: details of missing information".
For this particular error message - the sync will not happen again until the appropriate values for the state worked and the state subject to withholding are included in QBDT.
Go to QBDT > Edit > Preferences > Payroll and Employees > Company preferences > Employee defaults > Taxes > State.
Add the appropriate values for the state worked and the state subject to withholding.
Make sure QBPOS App and QBDT Company are open.
Wait for the sync to happen again (please note - this may take up to an hour).
If the issue persists, please contact Revel Support.