It's been live to pre order since Friday June 11th
It went live Friday red carpet was just before 9am and general sale was just before 12pm
You are 3 days late
You not going to have discount code work 3 days after a pre order going live
Discount codes are for in stock items only
You would have needed to be a red carpet subscriber and try as soon as it went live around 8.49am on Friday
Zavvi disable discount codes on pre orders before or shorty after going live as they not meant to be used on pre orders (Zavvi Terms and Conditions)
The only reason some red carpet subscribers manage to use a discount code on some pre orders is
luck as Zavvi have to manually disable the code on pre order listings
You would only had a few min at max to to use a discount code if it was working on friday morning at 8.49am