Hello @Anthony190,
Welcome to the Community Center.
In terms of coupon codes, they can expire if not used, so this might be the reason. Do you know how long you have had it since you receive the email stating it?
Also, just to check have you used this coupon before? If so, and you didn't use the full amount it is not possible to redeem the difference.
Here is a helpful Help Center article, which might help as well.
Let me know how you get on.
Lizzie
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