No Longer Able to Play Two Games At The Same Time?

I tried to launch Sims 4 while I had Sims 3 running. It's just easier for me to progress games at the same time or during down time in one game. When I clicked "Sims 4" play button, I got a message that I have a game running and a request to close that game first. Why is that? I own both games. I should be able to launch them since they are not the same game and they are not being launched from different devices with one EA account.