@ashleighlk
Are you logged in to Origin with the same user account you registered your original game with?
More importantly though, if you have the 2015 model MacBook Air with the Intel HD 6000 graphics the game is not compatible so you will be unable to run it. You can try the workaround here, substituting Intel Iris for your graphics card, which some have found successful. I have also read that just the base game with no EPs added on can work. Ultimately though your Mac is unsupported because it is far newer than the game ☹️