I had this issue (Game would launch and crash on the McLaren Senna window) since earlier this month (September 2020), I believe I have a workaround, it is a pain in the backside.
I can replicate the crash (hangtype:activation). It is something in the car pass, so don’t install any car packs.
I literally had to reinstall Windows. Start fresh, format the drive and re-install it (make sure you create a media creation tool first). Uninstalling the cars individually won’t work, I had to start from scratch.
On my fresh Windows install, I installed the game to my Windows drive, Launched it, Worked. Installed the VIP, Launched it, Worked, Welcome Pack? Worked. Then Installed DLC packs Fortune Island and LEGO, Launched = Worked. Installed the Car Pass, Launched…Hangtype:Activation.
I had to reinstall Windows AGAIN! Then repeated everything up to and excluding the Car Pass and all seems okay so far (knock on wood), it’s been a week.
I am not happy about this, it’s probably the worst experience I’ve had with a PC game, nothing has ever needed such drastic steps to work, it’s actually shameful.
Also, remember this worked for me, it may not for you, so it’s on you to take the risk and deal with installing all your programs again - make sure you backup your stuff before you do anything - making a list of installed programs helped me out.
Edit: Someone earlier in the thread mentioned Dolby Access (DA), I just want to mention that I had DA installed prior to FH4 and there seems to be no conflict between the two (for me).