What year is it? When you press the button on the tailgate you should feel the spring operate the contacts. If you are not feeling a click the copper spring has dislodged, you can fix it by taking it apart and remounting the spring plate.

 

thanks for the reply, how does the buttoncome away from the tailgate.?

 

Not sure on a Modus but on a Clio the card on the inside of the tailgate has to be gently prised off, (expect several of the button clips to break) and the trim holding the press button unbolted. Only do this if you are not feeling it clicking, compare by operating the button with another Modus or Clio.