Is the LED light illuminating?
When you take a puff on the device, one of the "G" badges on the device (either front or back) should immediately glow blue. This means the device is charged and functioning correctly.
If the "G" badge glows green upon use, the device is working but should be charged soon. If the "G" badge glows red on use, the device is about to stop working, and should be charged immediately.
If neither badge lights up on use, your device or charging cable may be faulty.
Is the LED light on your device illuminating?