How do I make an inactive employee active again

Make Inactive or Make Active is a basic list task you do in any list in QB. Open Employee Center and make sure, at the top of the names, it is All Employee; not only showing Active.

Now you see the left column with the X. Click and remove the X for that name.

If you put a Termination Date on that person, don't overlook removing that date.

Active or not = shows in the list and in dropdowns for selection.

Termination date = will not show in Payroll to be paid, after that date.

Two completely different functions.