Thanks @matthewritenburg, I tried it and it worked, that's my bad. I read on the PluginBoutique website that Vocalizer Pro doesn't work with Studio One and also found an old thread claiming that you couldn't send midi data to an vst, so I wrongly assumed that you just couldn't. Thanks for clearing that up for me. Vocalizer Pro works now as well as my other plugins.
Also, if anyone stumbles upon this thread and is searching for a good and free Vocoder, I can strongly recommend MidiChoir or La Voz Cantante. Just found them through bedroomproducersblog.com and to me they sound on par with some paid vocoders, certainly better than most free options.