there are many reasons why a student may be unresponsive. what solutions you would use to deal with a student expects you to dominate the lesson and do all the talking.
In a classroom situation that is oriented toward conversation, I find that direct but open-ended questions that touch on common experience are useful. Direct in the sense that you call on people and ask them directly (in addition to encouraging people to speak up freely); open-ended in the sense that the questions ask for an opinion or feeling about something without there necessarily being a right or wrong answer. Questions that relate to common experience are good because it virtually ensures that everyone will have some kind of answer.