Having just updated my Mac to OS El Capitan, upgraded my Cubase 6.5 to 8 pro and brought NI Komplete Audio 6 interface I am unable to get any sound or signal. Runs fine through internal but nothing through Komplete Audio 6? All files are up to date with Cubase, Komplete and mac? Komplete shows as the output bus correctly and is the drive in VST settings? Your help would be extremely appreciated as now spent two days trying everything! 
Hello,
We are recommending our customers not to update to El Captain, the same for Native Instruments and many other companies…
Unfortunately for you, it seems that you will have to wait until all the issues have been fixed, or you might want to find a way to roll back to Yosemite.
Best regards,
GN