If you are running macOS Sierra 10.12, or later, on your Mac and have iCloud Drive enabled then you may be having an issue with your saves. Is the game like new again every time you start it up and all your previous progress is gone? This will be because when you set up Sierra – whether as an upgrade, brand new install, or set up a new Mac – you will have been prompted to set up iCloud Drive. If you just ploughed forwards without reading the prompts, accepting everything the setup assistant was asking you (god knows we all do!) you will have set up your iCloud preferences to move your Documents and Desktop folders to iCloud. So every time your game loads it is recreating a brand new Sims 4 user data folder because it cannot find the original.
You can get round this by going into System Preferences > iCloud > iCloud Drive then click on the Options button and uncheck the box next to Desktop & Documents Folders:
This means that your Documents folder will stay localised on your Mac and not be pushed to the cloud. Your game will then happily be able to load your previous save from your Documents > Electronic Arts > The Sims 4 folder.
The following links explain iCloud Drive in more detail, including how to save your Documents folder contents back onto your Mac: