apply coupon box not working in basket or checkout page

Hi, We have a issue where the “apply coupon” box is not working in live basket or checkout pages that the customer will see. The box is visible on the page but when you click on it to add the code nothing happens.
If I go to the dashboard and go to Pages then Basket and then preview changes it works perfectly.
I have checked and the Enable the use of coupon codes box it ticked in the settings.
Any help will be very much appreciated.

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