If I recall correctly, if you installed Komplete 8 Ultimate prior to installing Sonar, the Komplete installation process will default to one path, but if Sonar was installed ahead of Komplete, the Komplete installation will default to the Sonar default plugin path of C:\Program Files\Cakewalk\vstplugins.
I would suggest you launch Sonar, and make sure that the path to your Komplete 8 Ultimate plugins is added to the Cakewalk Plugin Manager's search paths for VST plugins. Click on Options, underneath where it says VST Configuration, to see and adjust the VST search paths Sonar will use. Sonar should scan for new plugins automatically when you restart Sonar.
Bob Bone