Coupon not changing the figures in cart

I am running OC 1.5.6.4 and have used in the past a few discount codes created in COUPONS, however I am currently doing another for black Friday ( a little late now !) and it does not change anything, I have even tried using previously working codes and they do not work either ( with dates changed, yes )
Only change to store was adding an SSL certificate, but when I switch that off it makes no difference.
Can anyone shed any light on this urgently please, Thanks.

Have you made the coupon category or product specific? try a test one with unlimited uses per coupon and customer

Do you get a message when applying it? whats your website url