Hi,
I was experiencing the same issue! (I have the same computer as you are describing.) Try launching the Sims 4 application either from your applications folder, the desktop, or from the Origin app. When you are on the starting screen, click the three dots on the upper-right hand corner, and enter the "Game Options" menu. You should enter the "Graphics" tab, and in that tab, locate the "Display Type" option. Originally, it should say "Fullscreen". Click the drop-down menu, and select the "Windowed" option. It should fade into black and fade out to your desktop, and you should find that your Mac has gone back to normal. You can then change the drop-down menu back to "Fullscreen", and you can play as normal.
I hope this helps you or anyone else visiting this page!
