We have that exact same problem. So far we have tried every "Troubleshoot" and nothing has helped. No launch and not showing up on Ubisoft launcher as well. I think this will be our last attempt with Ubisoft. My whole family is just frustrated with not only the issue but the lack of help about this from Ubisoft.

Make sure your Steam account is linked to your Ubisoft account. Did you launch any other Ubisoft game from your Steam account? Do you have a new version of Ubisoft Connect installed on your drive? If not, download the latest version.Launch UC as administrator. Try launching the game from the UC library.

also try to launch from .exe. located where you installed game. with steam and Ubisoft launchers open.

Originally posted by Calypso:

What am I missing? When I bought an Assassin Creed game through Steam, did not have trouble adding them to my Ubisoft account...

Try opening the task manager, find the Ubisoft Connect process and terminate it. Then try launching the game again. I usually have to do this the first time I try launching a Ubisoft game after the last system restart.