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Little to no vapor production could be the result of many different issues, including the nature of the dry herb (fineness of grind, water content, loose or tight pack, etc.). If you have produced vapor with your herb using a different vaporizer, then the problem may be with how you are using the Legacy or the Legacy itself may be defective. Since the Legacy can be operated in two different modes - Session or On-Demand, be sure that you are achieving and holding your desired temp. Also, you should contact Airvape Customer Service if there is an issue with defective product.