Hello I recently switched PC's and have installed Sonar 4 (yes I know its old haha,I have Platinum also but it's new look is so confusing.) Sonar 4 is working ok but for some reason I'm missing the VST in the effects menu. I have the VST adapter 4 also seems to be working and has found all my plugins. But no VST in the menu at all. 

Have you populated the correct directory locations for the detection process to find them, long time since SONAR 4.  Most of us have been asleep since then.

Hi, and welcome to this forum.
As mentioned above, you have to add the relevant directories in SONAR to get the Vst's to show. I do not remember where in Preferences Vst settings was in SONAR 4.
Do you still have access to your old pc? If so, make sure you have the same scan criteria on the new one as you did on the old one.
Best of luck.