I had a lot of grief initially setting up Melodyne, but I contacted their support and they came back with this which ultimately fixed it all. The only thing I did was delete the folders that were left behind after the initial uninstall. So my overall instructions are:
Uninstall Melodyne from the computer.
Reboot the computer
1) Delete any Celemony folders you see under Program Files and your user area, for example:
2) C:\Program Files\Celemony
3) C:\Program Files (x86)\Celemony
4) C:\Users\YourUserName\AppData\Roaming\Celemony Software GmbH
5) C:\ProgramData\Celemony Software GmbH
6) Follow the appropriate section below
Delete any previously downloaded Melodyne zip or dmg files.
SECTION 1 If you DO have a Celemony Melodyne account
Log into your account
https://www.celemony.com/cgi-bin/WebObjects/LicenseApp
and download the Melodyne installer from there, (not from the Presonus website)
Quit Studio One (if it is running)
Install Melodyne 4 version 4.0.4.001 from the Installer
Start melodyne as a standalone application and click the activate button.
SECTION 2 If you DON'T have an account at Celemony yet :
Please delete all previously downloaded Melodyne zip or dmg files.
Please log into your Presonus account and click on “Claim Product Key” for Melodyne Essential
Copy the Serial Number you will see there (it is a Melodyne 4 Essential serial number)
With this number create a new user account at Celemony
https://www.celemony.com/cgi-bin/WebObjects/LicenseApp
by clicking on First-time registration.
Download the Melodyne installer from there, (not from the Presonus website)
Quit Studio One (if it is running)
Install Melodyne 4 version 4.0.4.001 from the Installer
Start melodyne as a standalone application and click the activate button.