"ElsieSimming;c-16414858" wrote:
I recently updated my Mac to macOS High Sierra (version 10.13.4). Before I updated my computer, I played sims like nothing was wrong. As soon as I updated it, it said there was no disc even though there was one.
Afraid that's the problem right there. As @puzzlezaddict said, the newer Mac operating systems are not able to authenticate the discs, it will always be as if you didn't even have one in the drive. TS3 disc installs and TS3 games that require a disc in the drive to play will not work on El Capitan, Sierra, or High Sierra and there is no known way to fix that (unless @Ashpeef found a way and has been keeping it a secret!) other than uninstalling everything and reinstalling the Origin version of the game.
Your ongoing saves can be preserved though by first pulling out the TS3 user game folder in Documents and using that to feed your new game folder with the required content, worlds, and sims (and mods) that you have installed, then ultimately your saved games.