I cannot think of any reason why they would not work in Professional. If you can use other third-party VST plugins, then Waves should work as well. In general, these are the most likely reasons they are not showing up:
1) They have been installed to a path that Sonar does not know about. Check to see where they are and make sure that path is listed in Sonar's VST scanner.
2) They have not been activated. Use Waves Central to activate your license.
3) The Waves installer failed with an error you didn't catch.
This last one caught me out early on when Waves Central first came out. There is a troubleshooting page at Waves website that will walk you through resetting a PC so you can install Waves products cleanly.
Regards,
Dan