This is an error or fault code, if it occurs during puffing it could indicate short circuit protection function, device temperaure too high or vape too long (either a puff of more than 5 seconds, or total of more than 40 seconds of puffing in a 60 seconds period).

If it occurs during charging, it could mean a charging fault or device temperaure is too high or too low. Charge the device in the recommended temperature range (15⁰ to 25⁰C) and use the recommended charging input (5VDC, 1.31A).