Why is my The Sims 3 PC game not working?

Yesterday, I installed the latest update for The Sims 3, not knowing it was a Mac-only update (I have a PC). After it updated, I clicked the "play" button on the launcher and it said "Your The Sims 3 base game is not compatible with this expansion pack. Please update your game via the game launcher." I went to the update section and it said "Your game is up to date". So, I searched some stuff on the internet on how to fix the problem, and somebody had a link to update the game to an older version. It updated the game, but now when I click play it says "You need to insert The Sims 3 Late Night expansion pack disc!". Late Night is the latest EP I have for The Sims 3, and I had bought it as a Direct Download through the EA online store. So, I do not know what to do. It will not let me play the game. Thank you so much if you can help.