I bought a waves multi-band compressor plug-in and Sonar Platinum doesn't find it when searching for new plug-ins....I've tried manually inserting the waves file into the VST folder but still no luck....TIA

Yes, they give it an obscure name "LinMB Mono" and "LinMB Stereo". Search for LinMB in the search bar in the plugins browser and you should find it.  Next problem is that you'll not remember this obscure name next time you want it, so using the manager, move it to where you know you'll find it next time, likely in [Platinum / Dynamics / Multiband]. I hope you bought it in the recent one-day deal like I did. It'll probably take me a few months to learn how to use it correctly.
 
Jerry

If you use the VST3 it'll simply be in the dynamics folder already. Assuming the installation went correctly.

I have it running now thank you...It was a faulty installation, once I re-installed it, the program showed up in the VST3  section...all is well now. and yes I did get it on the one day sale for $29...that seemed like a bargain for a Waves plug-in. usually $250....