Hey!
You're not doing anything wrong, this process should all be quick and easy.
After reviewing your account and I am unable to see the "Together Forever" achievement unlocked, which is what is acquired when completing Far Cry 5. Once this is unlocked you should then be able to redeem your reward.
You could try launching Far Cry 5 again while connected to the internet, to see if that syncs with Uplay.
If it does not work however, please provide us with an image of the Xbox Trophy "Together Forever" unlocked.


