The final piece in Ubisoft's 30th anniversary giveaway puzzle, Assassin's Creed 3, is now free for everyone. You can grab it from the Ubisoft Club (opens in new tab), but be aware that you might need to wait before jumping in. Apparently there are an awful lot of people who want the game, and going by the chatter on the Ubisoft Support Twitter account, the servers are struggling to keep up with the demand.
The good news is that AC3 will be free for a month, which takes us well into January, so if you can't get it today, there's always tomorrow, or the day after that, or sometime next week. Hey, it's been out for four years now. A couple of extra days won't kill you.
Owners of Assassin's Creed: Black Flag have been experiencing a separate, but apparently related, problem: After claiming their free copy of AC3, Black Flag simply disappeared from their accounts. Exactly why this happened isn't clear, and people have recently begun reporting that the game has reappeared, so it seems that Ubisoft is on top of the situation. I've reached out to Ubisoft to ask what's happening, and will update if I receive a reply. Meantime, if you've run into this issue, let us know if Black Flag has been returned (or not, if that's the case) in the comments.