It could be one of several safety, or battery-related, reasons:
• Vuse ePen automatically shuts down after 10 minutes of inactivity. Press the button 3 times in quick succession to reactivate your ePen.
• Your Vuse ePen may need charging.
• You may need to change your Vuse ePen cartridge.
• Dirt might be blocking the connection between the device and the cartridge. Just clean it with a dry cloth.
Please contact customer service if above suggestions do not solve the problem.