Thanks for you help - I figured it out finally 😕mileysurprised:
Turns out I went to the Origin screen --> My games and I could see my Sims 3 and Sims 3 Pet was grayed out. So I clicked on it and it asked me to connect to the internet. It is now downloading. I guess this wasn't clear to me, since I have the disc? I thought it was supposed to install directly from the disc? The game was already registered, and I didn't understand the next step. Once it is done downloading, I'm sure this game will finally play.... Thanks again.