I found it at C-> program files -> common files -> VST3 -> Celemony -> Melodyne. It's in the scan path but still no Melodyne region fx or VST3.
 
Rocky

And because of the error message shown in your OP, it never will either! Some program or other (even a 3rd party one for Sonar) has "broken" something. Same thing happened to me. So I did a re-install of an HDD image and I then got Melodyne and Region EFX back.  I still do not know what program after that image was done did the damage..I have not re-installed all yet - I have a su****ion it was AD2.
It may be possible to get the same result by deleting the Sonar installation in full (and also registry entries) then re-installing it.
Unless Sonar give us a full explanation of that error message and it's origins, I think this is about the only action that will fix it, drastic as it seems. I did ask them to explain it, but they seemed happier to be able to forget about it when they saw (via the forum, not their assistance) that my issue was resolved. There did not seem to be any alacrity in attempting to explain it!
 
EDIT: why is the word su****ion edited out???? phonetically - susspishion

joden
And because of the error message shown in your OP, it never will either! Some program or other (even a 3rd party one for Sonar) has "broken" something. Same thing happened to me. So I did a re-install of an HDD image and I then got Melodyne and Region EFX back.  I still do not know what program after that image was done did the damage..I have not re-installed all yet - I have a su****ion it was AD2.
It may be possible to get the same result by deleting the Sonar installation in full (and also registry entries) then re-installing it.
Unless Sonar give us a full explanation of that error message and it's origins, I think this is about the only action that will fix it, drastic as it seems. I did ask them to explain it, but they seemed happier to be able to forget about it when they saw (via the forum, not their assistance) that my issue was resolved. There did not seem to be any alacrity in attempting to explain it!
 
EDIT: why is the word su****ion edited out???? phonetically - susspishion

I had AD2 and Melodyne VST3 including region fx existing happily together on my machine prior to my Waves debacle. I'm considering an X3 reinstall at this point.
 
Rocky

Yeah, as deep as that sounds, I think it is the only option. If CW get back to me explaining that error message (which then means we may be able to track it down and ifx, with re-installing) then I will post the comments.