I just saw some people reporting the same problem in some other games. I found out the reason, it seems that Steam just changed the DRM, the old cracks no longer work with the latest versions of the games. In general, you can try to fix the following:

1. Go to the folder "...\Engine\Binaries\ThirdParty\Steamworks\Steamv157\Win64".
   
   
2. Delete the file "steam_api64.dll"
   
   
3. Change the file name "steam_api64.dll.bak" to "steam_api64.dll"
   
   

Now, you launch the game, it will work.