Invalid license. Reason code = missing DLL: Error 0xC1

I know it may seem like a pain in the *, and I've the same problem and yet to try this. But maybe just redownload the game. It's worked for other games for me on Steam, maybe it was just unlucky or something and a file got corrupt along the way. Anyways I hope this works for you and best of scrapping those Clanker!