That's the error, briefly the game was not booting saying I wasn't connected to Steam-when I actually was. Since then, the game won't boot at all. I am running Windows 10 Pro, Processor Intel Cor i5-2500K CPU @ 3.30GHz, 8GB of RAM, Geforce GTX 970 Driver verision 378.49. I haven't added any new software or hardware in few months. All MS updates are current.