You need to make sure that you have activated Melodyne in standalone mode prior to opening Studio One. If at any time, you upgraded Melodyne, you will have a serial number that differs from the serial number that is in your my.presonus.com account. You will want to maybe uninstall Melodyne, log into your Celemony acccount, and download the latest version. You will want to open that version in standalone mode and activate it using the code that is in your Celemony account. If you have any problems, you may want to reach out to Celemony to verify that you are using the correct authorization code with the correct build. Once activated, Melodyne should run in Studio One.