SOS

Okay, so I've been having this problem for a few days now.

I bought the Sims 3 and included were the Late Night expansion pack and the High-End Loft Stuff disk. I eagerly went to install Sims 3 (I started by deleting the files from the previous Sims 3 I installed on my Mac a few months ago), and everything seemed to be going fine. However, when I went to launch the game, it went through all of the introduction videos to only say that the disk was not in my computer. So after deleting the files, restarting my computer, etc. I decided to try Origin to play it digitally. I registered the game, entered the product code, all was well. However, when I clicked "Play," a message came up saying "Unknown error occurred." 

I don't know what to do at this point. Can someone please help? I don't want to be wasting my money!