I got the same thing as well. I'm sure there is a way to mod it to continue but I think the game ends as soon as you get 50 Provinces and destroy the Senate. I had revolts in 2 major cities and had the Julii cornered in one province. I was just about to wipe them completely out as I did to the Scipii and then it ended. I really would've like the chance to wipe out all the other Romans completely