I appreciate you for posting your experience here in the Community, @RPOII.
There are several reasons why a payroll item doesn't calculate on your paycheck. First things first, let's make sure that the latest version of QuickBooks Desktop and tax tables are updated.
Once done, you'll need to verify if the deduction payroll item is set to calculate based on Net or Gross.
To check how an item is set to calculate, please follow the steps below:
For additional reference, you can check this article for other recommended steps when a deduction item on a paycheck is not calculating: Payroll items on paycheck are not calculating or are calculating incorrectly.
Please let me know how it goes by adding a comment below. I'll be around to help ensure your payroll deduction calculates accurately. Wishing you and your business continued success.