I just upgraded to Sonar Professional partly because of Melodyne, but the software keeps wanting to be activated. I have done so using the serial provided be Cakewalk and it is accepted at the Celemony site, but yet neither the standalone or the plugin will accept it and keeps asking me to activate. Anyone tried this and have a good idea ?

I think it works now. When I registered, Celemony told my to download the latest version, so I removed that one and reinstalled the one that came with Professional and it seems to stick.

yes - that was the fix. had the same experience