We have become aware of an issue with Xbox One users being able to claim their Ultimate Edition rewards. You will need to install the Doomsday Pack again. You should be able to search for it directly in the Microsoft Store. If that is not the case, you may find it in the 'Related' section of the Ultimate Edition page on the Microsoft Store.
Once it is reinstalled, launch the game and you will receive your jacket, combat helmet, and bonus prestige. Please submit a ticket if you are still having problems accessing the content once you have the Doomsday Pack installed again.