All of a sudden lately in platinum when I select a clip and add regional fx - melodyne, then the editor opens but if I select a blob as if to move it... I can't hear it? as in hearing the pitch changing. if I move it and play back I hear that it has changed, but I can't tune by ear if I can't hear the note WHILE moving it. I did a support ticket with melodyne and corresponded with them. They determined it to be a sonar issue. Last week I updated both melodyne and sonar to the latest versions and the issue still persists. Any ideas guys?

I have that issue with Melodyne too ( full paid version).
 
Here's the rub: it's not repeatable in my case. 
Approx 10/1 ratio of times when it works as expected, then suddenly grabbing blobs produces no sound.
 
And yes, if you're sometimes tuning by ear and not just snapping to pitch grids, this is a major work flow buster.
 
I have found no pattern. 

If that is the case, (and I was about to upgrade from essentials to the full version) I think I will need to go with antares auto tune instead. I can't have it just be mysteriously inoperable on some projects when I am working with clients.

There have been a few threads about this issue in the last few years, so you're not the only one who has run into this.
A few things to try:
 
Make sure the track is in focus
In Melodyne Editor is Options>Note Editor>Monitor When Editing Blobs ticked?
In Sonar, try toggling the global fx bypass button **(this is the one that always works for me when I have this issue)

noynekker
There have been a few threads about this issue in the last few years, so you're not the only one who has run into this.
A few things to try:
 
Make sure the track is in focus
In Melodyne Editor is Options>Note Editor>Monitor When Editing Blobs ticked?
In Sonar, try toggling the global fx bypass button **(this is the one that always works for me when I have this issue)

Thank you, I will give this a shot!

I'm reaching here but want to say if the track you are Melo'ing is solo'ed you won't hear the blob. This has happened to me and I'm pretty sure that unsoloing the track made the blobs audible.

Try turning the Global FX button on and off. This worked for me.  

Turning the global fx off, then back on, seemed to work for me. Thank you Noynekker!