Java writeObject is writing an empty ArrayList

I'm having trouble writing an ArrayList of a custom class to a file. I'm using

public static void SaveEmployees() throws FileNotFoundException, IOException{
    ObjectOutputStream save = new ObjectOutputStream(new FileOutputStream("magicscheduleEmp.sav");
    save.writeObject(employeeList);
    save.close();
}

Where employeeList is declared and initialized as an ArrayList of Employees (my class) in the main method. I have definitely added objects to employeeList, but calling SaveEmployees writes an empty ArrayList to the file. The Employee class is serializable.

What am I doing wrong?

Edit: employeeList is initialized here (in the main method)

    public static ArrayList<Employee> employeeList = new ArrayList<>();

and populated through user input (in another jFrame class)

    if(MainUI.addempcheck == true){
        Employee newEmployee = new Employee(LastName.getText(), FirstName.getText());
        newEmployee.position = EmpType.getSelectedItem().toString();
        MainUI.employeeList.add(newEmployee);
        MainUI.listModel.addElement(newEmployee.writeName().toString());
    }
    try {
        MainUI.SaveEmployees();
    } catch (FileNotFoundException ex) {
        Logger.getLogger(NewEmployeeUI.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(NewEmployeeUI.class.getName()).log(Level.SEVERE, null, ex);
    }
    this.dispose();

I have a button which prints the contents of employeeList, and shows that the list is populated before I save it. Maybe it's a problem with calling SaveEmployees?