You say that your client does open on High Sierra? I literally updated to Mojave because I thought it was because I was still on High Sierra or something along those lines, and still nothing. I've double checked to make sure the steam client I have is the 64 bit, after deleting and re-installing twice. I've done everything just as the last guy said, and still nothing. If it is indeed 64 bit, there's something else going on. While you've got it bouncing away in the dock you can check this on your machine by going to Applications -> Utilities -> Activity Monitor -> and looking for it in the Disk tab to see if it's 64 or 32 bit. I have the latest version and it's 64 bit. Originally posted by ShannonApple:Are you sure? The latest version should not show the 'Steam is not optimised' message because it is 64 bit.
