PHP no output on frontend

i have a page where people can register for courses. some courses have the option to pay in rates. if this option is set, the value is shown in the sign up form. there should also be a checkmark that can be checked if you like to pay in rates. but this checkmark just doesn't show in the form.

here is the whole code of the form (the line that doesn't show up in the frontend is on line 486): enter link description here

and that's how the frontend looks (the checkmark should be shown in between the two other checkmarks):

enter image description here