maybe you have a diffrent ubisoft account
and you have registered the game on that account, im in the same boat myself and cant remember the account i activated the game to
screw ubisoft for this

so I went through about two weeks of back and forth with ubisoft support, during which they asked me for screenshots from steam, screenshots from connect, I uninstalled and reinstalled EVERYTHING from steam to the game to ubisoft connect *at least twice* - they had me screen record myself trying to launch the game, and post it to an unlisted youtube video, as proof - I deleted my caches, I zipped up my caches and my logs and my user config files and sent them - it was just hoop after hoop after hoop after hoop to jump through, each message in somewhat broken english, each from a 'different' support staff, I NEVER spoke to the same person twice the whole time I was messaging with them - and if there was even a two day lapse in communication, they would immediately automatically close the ticket as 'solved.'

FINALLY they made whatever change on their end, that they should have just done initially - and after all that, I could get into the main menu, but it required a remote server connection *for local couch co-op gameplay*.

I'm sure my support ticket is now closed and counted as solved and a job well done - but the truth is they finally ran me off by attrition.

I was never a huge ubisoft fan before, but I am ♥♥♥♥♥♥♥ DONE with them now. I don't care if they somehow manage to release the best assassin's creed game ever this year, they're never seeing another cent from me. I've got other games to play and other companies that won't ♥♥♥♥ me over.