I need help starting Tyranny of King Washington.

I bought the DLC on Steam through the Season Pass. I entered the code through the UPlay application. I open the game. Select "Tyranny of King Washington," but the only thing that happens is a message appears saying, "The Ubisoft server is not available at this time. Please try again later."

I've been trying again later for the last five days. Same message when I go to extras. I need help, this is pissing me off. Thanks!