How to install and License Melodyne 4?

I don't use Melodyne very often, but I want it to be up to date if I need it.
I read in the "SONAR 2016.12 Update" newsletter about the "Free Melodyne 4 Upgrade" back in January.
I have Sonar Platinum with lifetime membership and Command Center shows everything is up to date.
In the Cakewalk Store it shows Melodyne Essential with a date of 11/28/2013. 
I reviewed the list of "Available Downloads" and do not see Melodyne.
 
If I try to add Melodyne to a track, it pops up the license request. I insert my serial number and it says "Melodyne essential 2"
When I click continue to license it, it responds "Server Error Code 113 Product Version Not Acceptable".
 
How do I install and License the current version 4 of Melodyne?
 

I was confused by the FAQ: https://www.cakewalk.com/Products/SONAR/SONAR-FAQ#Melodyne
which says "I already have Melodyne 2 Essential from my SONAR purchase. Will I receive an update to Melodyne 4 Essential?  Yes. All you need to do is to run the “Update Check“ from within Melodyne’s preferences and it will guide you through the update process upon which you receive a new installer along with a new serial number from Celemony."
 
From the Melodyne 2 plug-in (which will not accept my serial number), then Setting / Options dialog, check for update.  It says "This Version: Melodyne Playback Mode 2.1.2. b 2 64 bit.  No Newer Version Exists"
 
You are correct about going to Celemony's site - that is how it actually works. After logging in, I was able to download the installer.  I closed Sonar, ran the installer, opened Sonar, (the VST scan identified the new plugin), then I loaded the project with Melodyne on a track.
 
The plug-in would not function or open from the existing track.
I discovered it is necessary to delete the plug in from the track, and then insert it again. At that time, Melodyne opens and must be activated.