For Forza Horizon 4 players, this guide is aimed at those who had their Forza Horizon 4 not launching on Steam at all. Let’s check it out.
If you didn’t use BitDefender or didn’t have non-latin characters in your username and the game still doesn’t launch for you completely without any error box – you might want to try this as a potential FIX.
A keen eye might notice that official troubleshooting guide from Forza Support Team mentions reinstalling Microsoft Visual C++ programs, but they only reinstall the most recent version, which is not enough to fix the issue.
Press the Windows Key + R, type appwiz.cpl and then press Enter


This my seem like a lot, but they actually uninstall pretty quickly (your mileage may vary though)

https://www.techpowerup.com/download/visual-c-redistributable-runtime-package-all-in-one/
This is the key part of the guide, because it seems that Forza Horizon 4 actually needs one of the older versions of VCRedist Visual Studio C++ runtime, possibly even an x86 one.


Wait for the installation process to complete.

Your PC might need a restart, which wasn’t required in my case.
If your error matches what’s described in the guide info box and this FIX didn’t work for you, please let me know.
It didn’t work for me. I also tried temporarily turning off bit defender and still nothing. I also checked my game files and they are not corrupt.