@JulianGerhard is correct, your bot will not train an NLU model if you only have one intent. Therefore it will not classify the intent, and it won’t know how to respond to that.
As for
if 2 intent, 2 stories, once the chat is done once, the next time it is chat it will not return any messages
If you want to be able to go back to the beginning after, you could try changing MemoizationPolicy to AugmentedMemoizationPolicy. However, know that if in the future, you have slots set, this could affect the second conversation. In that case, you’d want to start over via /restart like Julian recommends.