Welcome aboard to the Community. It would be my pleasure to help you get to the bottom of this strange behavior going on with the Vacation time in QuickBooks Desktop.
There are a few things we need to check to determine why it's not accruing vacation time on one of your employees.
Here's the list:
For the detailed steps about the process, please visit the article I recommend on this:
Sick and vacation time incorrect or not accruing on paychecks.
I want to ensure that we'll be able to figure this out, so please feel free to let me know how it goes. If you should have any questions, I'm just a click away.
If you edit the employee and review the sick and vacation settings, what is the accrual rate and frequency? If per check or hours, then not sure. If annual or there is no accrual amount, then that is what is causing what you're seeing.