Hi,
sorry to hear that. Which Melodyne version are you running? OSX or Win? We need this info to track down the problem. Meanwhile you need to reset the vst support.
On OSX please remove the folder
/Users/YourName/Library/Application Support/Steinberg/VST Connect Performer
On Windows please remove the folder(s)
C:\Users\YourName\AppData\Roaming\Steinberg\VST Connect Performer
C:\Users\YourName\AppData\Roaming\Steinberg\VST Connect Performer_64
See you,
Michael.