Have you tried uninstalling it, ( after steam uninstall go to the steam WF&S file location and completely deleting any remaining files) and re installing it again?
Steam uninstalls never really deletes every single file
And if that does not work, I would try to get into contact with steam support
i noticed that there servers can be very often too busy to download a game i just bought but its funny they have less busy servers when im buying. i have no other problems with steam apart from that.