If you GPS suddenly won't turn on, respond to any input, or show as charging when plugged in, it may be frozen. The GPS might still be recognized as USB storage on the computer, but it will not respond in any other way. When this happens at the boot stage there is unfortunately nothing that directly indicates this problem, but it is the most likely issue.
The only remedy for this is to let the GPS discharge the battery to reset the unit. The GPS should be left unplugged, and it should drain the battery in a day. Then it will take a charge and power on again.
This is usually an isolated event, but if it starts to happen regularly, there may be a memory corruption issue. In that case, we'd recommend force updating the GPS to reload the firmware, and then restoring the device to factory defaults to reformat the internal storage. You can transfer your Lezyne folder on the GPS USB storage to your computer to save the ride data, but the folder should not be copied back onto the GPS. It will have to be set up as new.
If you have further issues, please feel free to submit a request for help from our Support Team.