I had a problem. What worked for me was to send my Waves licenses to the cloud, completely uninstall Waves,
Start Sonar and rescan so it removes Waves from its plugin list, reinstall Waves, send the licenses from the cloud back to my computer, Start Sonar and rescan plugins. Works fine now. if you have any Waves demos that are expired get rid of those. An expired Waves demo prevented my vst scan from completing.