Re: Sims 4 Mac keeps crashing on initial loading screen with update for how to fix

Your Mods are in the folder on your Desktop, as are your saved games and CC. Since you said the game worked again, it leads me to believe that one of your Mods or pieces of your CC is out of date due to recent updates. Check the sites that you have downloaded your Mods and CC from and check to see if the Mods/CC have been updated to work with the current updates. You should turn off Automatic Updates in Origin so that you can check to make sure your Mods are updated to the latest patches before you update. 

Before adding everything back into your game, you should add only a few pieces back at a time and see what may be causing your game to not start up.