getting “Error 51” trying to start the game thru steam after the patch. Any ideas ?
One of search results: https://gaming.stackexchange.com/questions/350808/error-code-51-when-launching-a-game-using-steam
thank you, i have gone thru all the steps 
and still same problem.
See if anything here helps
https://steamcommunity.com/discussions/forum/7/1736588252372581015/
Have you verified your game files?
Tried it all, gonna go thru it one more time thou in a diffrent order.
I had the same issue. I’m using F-secure for anti-virus software and I had to add the steam directory to the excluded list for the game to work.