Most likely you have the latest version of SDK. I had to open my SDK for it to update. Might want to make sure that is up to date...but I am guessing that if you are able to get into the game, it is probably working. Worth a try anyway. Secondly, if that doesn't work, I would try re-downloading the mod from a different location on the web and reinstalling fresh. Make sure you delete all the files in the sourcemods folder. That might solve your problem. Let me know how it goes.