Hi there!
If the the previous answer did not work for you (Completing Article 5 again and do not skip any cinematic)
And you are yet to received the reward for completing the Blacker then Black challenge, please could you go to our support site and create a case by scrolling down to the bottom of this page provided and click on 'Contact Support' -
https://support.ubisoft.com/en-GB/
Please provide us with your Ubisoft account username, the platform you play on and a screenshot of you logged into your account showing the situations with 3 stars and we may be able to help you unlock the challenge.
... Read more
If the the previous answer did not work for you (Completing Article 5 again and do not skip any cinematic)
And you are yet to received the reward for completing the Blacker then Black challenge, please could you go to our support site and create a case by scrolling down to the bottom of this page provided and click on 'Contact Support' -
https://support.ubisoft.com/en-GB/
Please provide us with your Ubisoft account username, the platform you play on and a screenshot of you logged into your account showing the situations with 3 stars and we may be able to help you unlock the challenge.
... Read more