Why did your chatbot fail miserably ?

Neo is a talented developer who loves building stuff. One fine morning, Neo decides to take up a road, less travelled, decides to build a chatbot! After a couple of keyword searches and skimming through dozens of articles with titles "build a chatbot in 5 mins", "chatbot from scratch" etc, Neo figures out the basic components to be intent detection, Named Entity Recognition,Text Matching for QnA . Another 30 mins of Google search and Neo has collected his arsenal, the state of the art implementations for these 3 components. His arsenal has the almighty Bert for NER, Ulmfit for Text classification, RoBERTa for text matching.