This is weird! How about this?
Do you know how to scan your VST folder(s) and also organize them using custom lists? If so, then I would 1) make sure all your VST folder(s) are "pointed to" and scanned, including the Sonitus:FX Suite folder which may be separate than Sonar's defaults--set this up in Preferences; 2) manually re-scan the folders(s) in Preferences or use the little, downward-pointing arrow on the top of the Browser [this is important in subsequent steps]; 3) Within the menus of that little arrow, create a new custom list for audio-FX plugins by selecting "Manage Layouts"...within the utility window, find the Sonitus:FX Suite plugins and add them into the list; 4) Save the list; 5) in the Browser first go to Default All Plug-Ins then choose your new, custom list; 6) Try the Sonitus:FX Gate or Comp.
Hope that works!