Did you redeem the coupon-code, and recieve the e-mail with the game-keys for each game title? I want to clarify that, because it alsmost seems as though you're trying to enter the coupon-code on UPlay.
I read in another post that someone was able to resolve their issue by using a different UPlay account. I believe the game-keys are regionally-based, so as a suggestion, make sure you are logged into the correct regional account.
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