I think the US billing address was the issue as I was trying with a US VPN and didn't work.
Ubishop can be a disaster, I remember I activated AC3 for a friend but it didn't appear in the games tap until 2 week later and many communications with Ubi support.
Thanks again for the help, I...
it's the region. I got a code from a CAG and couldn't activate it myself. Had to give him my Uplay info and he activated it for me.
Good thing he was a trustable CAG, otherwise it would've been a frustrating experience.