I am not sure but I guess Vocoder is in the MMM 17 Premium version because it is in the Music Maker 16 Premium version  but not in the standard version of MMM 16. As I use MMM 16 Premium I can advice according to that please try and see.
You can apply any method to see if Vocoder is in your program or not.
Click Start button (usually on left below Microsoft logo round button) All Programs/Magix/Documentation. Documentation is a pdf help file. Open it try to find about Vocoder.
Or
Drag and drop any object(audio) on the arranger then put cursor on it and right click. From the menu click Audio effects then locate Vocoder (Shift+C)

nihon94