Hi,
Make sure you have the latest plug-in update installed. Make sure the latest iLok driver and PACE software is installed.
Make sure the Waves plug-ins are installed inthe default Cubase VST folders (or any subfolder). Few days ago, there was a thread on the forum, only these flders are working for Waves plug-ins.
Btw, are the plug-ins licensed already? See this thread, please.