A: It is not compatible with OSX Yosemite.
Native Instruments made some updates to their effects plugins in the past year. NI recently released several statements addressing Komplete Players 1-7's compatibility with OSX Yosemite. In the conclusive statement addressing this issue, NI states "KOMPLETE 7 and earlier versions of KOMPLETE (including versions of KOMPLETE ELEMENTS) are not supported on Mac OS 10.10 Yosemite (and forthcoming versions of OS X)".
On January 17, 2014 PreSonus released the following statement:
*Current PreSonus customers who have already registered Studio One and may be upgrading, may already have a Native Instruments key for Komplete Players 7 (Artist) or Komplete Elements 7 (Producer and Pro). If you would like to upgrade your version of Komplete Players/Elements, you will need to install the latest version of the Players found at: http://www.native-instruments.com/en/products/komplete/bundles/komplete-players/ This will upgrade your version 7 software to version 8.
NOTE: If you have not created an account with Native Instruments, please do so now.
Creating a Native Instruments Account
• Go to: http://www.native-instruments.com
• Click on the login link on the upper right hand corner of the site and choose "Create Account".
• Enter your credentials and hit Create.
• Look in your email for your username and password.
• You will need the username and password for the NI Service Center activation.