SIMS 4 MACBOOK ERROR Unable to start: The Sims™ 4 is already running.

So I'm playing Sims 4from an external hard drive, and I just finished downloading the new updates from the game. However, when I tried to open the game, I got this pop-up message although The Sims 4 isn't running. I have ticked all boxes under System Preferences > Security & Privacy > Files and Folders > The Sims 4, and I've also given Full Disk Access to the EA App. I also deleted all my Mods. Does anyone know how to fix this? 

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