Re: The Sims 4 on Steam will not open whatsoever.
@DaniJam05 Please try running both the EA App and Steam as an admin: right-click each desktop shortcut and select "Run as administrator." If that doesn't help, uninstall the EA app with Revo Uninstaller (the free version is fine) and restart your computer, then reinstall it.
If that doesn't help, please run a dxdiag and attach it to a post.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/
Please also let me know whether you see an error at any point when you're trying to run Sims 4, and if so, either post a screenshot or write out the full text.