Request Campaign rest api

Hi Guys,

I'm trying to trigger a smart email campaign using the rest api. Everything is set up following this guide http://developers.marketo.com/blog/sending-an-email-with-dynamic-content-from-marketo-using-the-api/

I've already added the Campaign is Requested trigger and is set to Web Service API but keep getting this error message:
"errors":[{"code":"1003","message":"Trigger campaign needs to have a 'Campaign Requested' trigger"}.

I have no problem running Get Lead By ID, Get Campaign By ID rest api. 

Any ideas?

thanks
Vinh