did you ever find a solution to the issue?? I'm having the same problem.
I have been playing the Sims4 for years. i have purchased every single expansion and game pack in addition to several of the stuff packs - all individually. My Mac just updated and I am getting that message as well - it says that the application is already running and will not open. I have invested hundreds of dollars into this game over the past few years and will demand a full refund if this does not get fixed. I have now been on hold with tech support for over 30min after waiting over an hour for a call. This is absolute BS customer service.
@radiokarma79 Move your Sims 4 game folder out of Documents\Electronic Arts and onto your desktop. When you launch the game again, a clean folder will spawn with no content. You should be able to load it without getting the error again, at which point you can quit and move the contents of your Saves and Tray folders (plus Mods if you use them) from your old Sims 4 folder to your new one.
That was super helpful! Thanks
