How I fix this?

[Pr0Dr1v4rBR]

(My Sony Vegas is in Brazilian Portuguese)

[Evauation]

@otomad

Vegas Pro 15 will be missing some api features that the script can't support, quoting from old patch notes.
Elastique & Classic pitch change. Change tuning method. Some PV rhythm visual effects and Reserve Formant, among others.

My only suggestion is to have the Audio setting turned off.

[otomad]

No, it is duplicate of #24. @Evauation @Pr0Dr1v4rBR

You're using the Vegas Pro 16+ Version of Otomad Helper on Vegas Pro 15.

This is what you should be using: 
https://github.com/otomad/OtomadHelper/releases/download/v4.31.28.0/1_otomad_helper_v4.31.28.0_vegas1415.zip