[CURRENT ISSUE] Sims 4 already running

I installed the Sims 4.  I went to play and it tells me the program is already running.  I can't see it, and I've tried to find it to shut down, but the only thing that comes up is my request to play.  nothing more.  How do I do this.  It's like it's running in the background?   Your help is much appreciated. 

Thanks,

Nancy