If you have been trying to connect to Uplay and haven't had much luck, you aren't alone. Ubisoft's online service is having some major issues.
Ubisoft Support has been tweeting about the disruption in service intermittently for at least the last six hours. The latest tweet said they are still working on the problem. Oddly, the official Uplay Twitter account mentions nothing about the problems. Ubisoft isn't detailing whether the outage is an internal one, perhaps a DDoS attack, or just high demand for a free copy of Assassin's Creed 3 as part of Ubisoft's 30th anniversary. Whatever it is, there hasn't been a quick fix.
Also within the last 24 hours, the company had to deal with PS4 connectivity issues, which were eventually resolved. And the Ubi30 anniversary site also was experiencing errors. Whether it is all related is unclear, but it has been a rough 24 hours for the Ubi support staff.
If you miss grabbing AC3 because of the Uplay issues, rest easy. The deal will be on until January 4.