When I add or delete a slot in my interaction model. A specific slot stops taking input and responds with with a beep sound when I speak the utterance of that slot then it takes the value and flow runs smoothly. To work it properly I usually delete and add again that slot then it works properly takes value without speaking the utterance. It is getting annoyed when a new slot or change in model is being done I possess to delete that specific slot and then add again.
Source: amazon.com