Here is what happens when you plug a Kobo device into power:
- If it is off, it will turn on after a short period. Exactly how long probably depends on the battery state. But, usually it is less than a minute.
- If the device is sleeping, it will wake and prompt whether to connect to the PC.
- If the device is running, it will wake and prompt whether to connect to the PC.
- If plugging into a charger (not a computer), whether the prompt happens depends on the charger. Some chargers to do not have whatever is needed for the device to think there is a data connection. I have never seen one, but, they have been mentioned here.
- When plugged in and just charging, the device can go to sleep.
Anything else is a problem. The charger that caused the device to flicker between connecting and not, would be assigned to the "roundfile". With prejudice. Though I would check the cable just in case that was the problem.