After helping people with the game a bit I decided to compile a list of solutions to most common problems. Don't forget to read the last paragraph!
Unable to start: The contents of your user data directory were created by a newer version of The Sims 4 and cannot be loaded. Please update your game via Origin to play.
There are only two safe solutions - deleting Documents\Electronic Arts\The Sims 4 folder (you will lose all saves, mods, options, etc.) or updating your game. Don't listen to people who tell you to delete GameVersion.txt or Default.ini file, they are idiots.
See the instructions page if you don't know how to update your game.
An attempt was made to access a socket in a way forbidden by its access permissions
or
Origin seems to be running. No communication with Orange is possible
Close Origin and make sure the game is not running. Add Game\Bin and Game\Bin_LE to anti-virus exception list, block TS4.exe and TS4_x64.exe in your firewall. If that doesn't help reboot your PC. And if that still doesn't help remove virtual network adapters if you have any. The game connects to the crack/Origin on port 3216 so it's something with your network.
The application was unable to start correctly (0xc000009a)
or
The code execution cannot proceed because OrangeEmu.dll/OrangeEmu64.dll/anadius64.dll/anadius32.dll was not found
or
TS4.exe/TS4_x64.exe is missing
Add Game\Bin and Game\Bin_LE folder to your anti-virus exception list and restore missing dll/exe from quarantine.
Origin is currently not running. [d3382ced:984c6a38:00000000:00000000]
Allow loopback/localhost/127.0.0.1 connection for the game exe in your firewall. If you can't find that option, allow all internet connection.
If you're using a VPN it may mess with the crack too, try disabling it.
Hello ;)
If you're using normal (64-bit) version of the game:
Game\Bin\OrangeEmu64.dll has some anti-tampering protection that gets triggered and you need to replace it with a version without that protection (you can also follow the steps for Legacy Edition below but this solution is better). Grab that file from the It Takes Two CODEX crack. That .dll alone can be found on crack only download page.
If you're using Legacy Edition (32-bit):
Don’t start the game in virtual machine (cloud PCs like Shadow count as virtual machine!) nor in Sandboxie (and the like).
Go to Control Panel > Uninstall a program > Turn Windows features on or off > uncheck Hyper-V. Uncheck Windows Sandbox if it's present too. Reboot your PC twice (important!) and check if the game works.
In Windows Defender Security Centre open:
1. Device Security > Core isolation details and disable Memory Integrity.
2. App & Browser Control > Exploit protection settings > Program Settings > Add program to customize > Add by program name, type TS4.exe (or TS4_x64.exe if you want to run the 64-bit version) and press Add. In the next window check Override System Settings for Control flow guard (CFG) and Force randomization for images (Mandatory ASLR), and keep them off. Click Apply and reboot your PC.
If that doesn't help, disable virtualization in BIOS/(U)EFI.
The application was unable to start correctly (0xc0000142)
or
MSVCR100.dll/MSVCP100.dll/MSVCR120.dll/MSVCP120.dll/MSVCP140.dll/VCRUNTIME140.dll/api-ms-win-crt-*.dll missing
or
Initialization error at start up. [135dec40:3fbbecd0:00000064:000000]
Uninstall any Microsoft Visual C++ Redistributable 2010, 2013, 2015, 2015-2017 and 2015-2019 you can find (both x86 and x64). Reboot PC. Install VC Redists (both x86 and x64) from those links:
VC Redist 2010
VC Redist 2013
VC Redist 2015-2019
If that doesn't help uninstall VC Redist again, reboot PC, delete MSVCP120.dll, MSVCR120.dll, MSVCP140.dll, VCRUNTIME140.dll and similar files (like MSVCP120_<something>.dll) from C:\Windows\System32 and C:\Windows\SysWOW64, reboot PC again and finally install VC Redist from those links back. Don't use crappy shit like Revo uninstaller because it only messes things up.
The application was unable to start correctly (0xc000007b)
Enable .NET Framework. Go to Control Panel > Uninstall a program > Turn Windows features on or off > check any .NET Framework you see. After that reinstall VC (see above).
Initialization error at start up. [135dec40:90f690cf:00000075:495f32a0]
Download language files.
Initialization error at start up. [135dec40:69731fb6:00000068:00000000]
Reboot PC.
Initialization error at start up. [135dec40:29f00e76:00000084:18a1dd51]
Remove mods and CC from Documents\Electronic Arts\The Sims 4\Mods.
If that doesn't help try the solution for error [ed35e0ea:29f00e76:00000000:18a1dd51] listed below.
The Sims 4™ is already running [ed35e0ea:29f00e76:00000000:18a1dd51]
or when nothing happens when you run the game
In Windows Defender Security Centre open Virus & threat protection > Manage ransomware protection. Either turn it off completely or click on Allow an app through Controlled folder access > Add an allowed app and select Game\Bin\TS4_x64.exe (or Game\Bin_LE\TS4.exe if you want to run the Legacy Edition).
Right click on Documents > Properties > Security and make sure your account has full access to that folder. If that doesn't help, create new Windows user and use it to play the game.
Can't run The Sims 4 with the video card in this system. [0e6d1221:1df4e8dc:80010000:00000000]
or black screen
or just crash
If you installed your game to a path containing a semicolon (;) - move it somewhere else.
If you have Razer Chroma or Razer Synapse - uninstall them.
If you have RivaTuner Statistics Server, activate Custom Direct3d support. If you don't, or it doesn't help, open Documents\Electronic Arts\The Sims 4\Options.ini and change the value of windowedfullscreen to 1. If that still doesn't help, change values of:
resolutionwidth to 800
resolutionheight to 600
fullscreen to 0
Infinite loading screen
This is mostly caused by bad mods/cache but sometimes because of bad graphics card drivers. Download the newest ones and perform a clean installation!
If you have a different problem
or suggested solution didn't work
Go to Documents\Electronic Arts and move The Sims 4 folder to desktop - this will start the game fresh. Run the game. If you still get the same problem - run the validator.
If starting the game fresh solved the problem - copy your saves folder from The Sims 4 folder you moved to desktop, to Documents\Electronic Arts\The Sims 4. Run the game. If you still get the same problem - it's corrupted saves. When you click on "Load Game" on the main menu screen there's an option to restore previous version of your save. Try it, maybe you're lucky and older version of your save is fine.
If the game works fine with just your saves - you can try copying other folders. Tray folder has items in your Library, it should be safe to copy it back. Screenshots and videos are safe too.
And finally - Mods folder. There's a high chance your problem is mods related and your game will break again after you copy them back. If that happens - use the 50/50 method to find the broken mod.