Initially you'll want to reset your Steam config for CPUCores as listed here: http://i.imgur.com/i1I9kV8.png Make sure you follow the directions, as in, after clicking that option, close CPUCores. Then close Steam completely. Then start Steam and then start CPUCores via Steam.

Just in case you have a very funky Steam Library setup and all your games aren't being detected, you can add the library directory manually into CPUCores.

See here: http://i.imgur.com/94D9XMS.png

1) Open CPUCores via Steam
2) Go to Advanced -> Steam
3) Click on Manage Steam
4) Add each library of games that isn't be detected with the steamapps root as seen in the screenshot ( http://i.imgur.com/94D9XMS.png )
5) Close CPUCores and restart

Done!