If the employee record has been marked inactive follow the below steps to reactivate them:
Note: If an employee has been terminated via Payroll please follow this article for steps on how to reinstate them.
1. Go to Lists.
2. Select Employees.
3. Click Employees.
4. Tick Show Inactives.
5. Click Edit next to the employee.
6. Select System Information subtab.
7. Uncheck Inactive check box.
8. Click Save.