Struggling with Yes/No Intents with Gogle Assistant Voiceflow?

Hi, I am trying to use Yes/No choices (with my extensions inserted) in Google Assistant Voiceflow and am having problems getting it to work, even when the simplest case (Sì=Yes or No). With Amazon Alexa I have never had any problems! Can anyone tell me why, if it has happened to them? Thank you very much!
PS Also No Match seems to act kind of weird…selected language is in Italian, but the assistant starts to speak as an English trying to read Italian!