So I did everything I was supposed to, but the plugin is telling me that I'm on demo mode and that it'll mute the output after 10 days. Does the crack that I downloaded keep the sound from being cut off or did I download it wrong or is there a way I can get a serial number to authorize it? If anyone has a clear answer, please let me know because I'm already using Vocal Synth and I really don't want my tracks to be muted.

 

Seems that you failed in the installation.
If you run the plugin on macos, procedure is the usual one: run the installer and then copy the k'd vst or component plugin into the plugin folder. I'm not sure about win installation, someone here will help you.