Coupon discount is not deducted from final total.

-- url of the page with the problem -- : timmcneilwines.com.au
-- HikaShop version -- : 1.5.7
-- Joomla version -- : 2.5.7

HI,

I have a rather old website that client was using very happily for a while now. We have tried to create a coupon we could use for Christmas special, but for some reason when added, the discount appears in the charges calculation but is not deducted from the final amount. (see the screenshot)

I haven't seen this issue before and am not sure if this is a settings option or not.

Updating the Hikashop version is not really practical as we would have to update the Joomla as well ( client cannot afford that at the moment).

Thanks!
G.