Check that the device LED lights up, flashing red during charging, steady green when charging is complete.
If the LED does not light up, check that the magnetic connector on the USB charging cable is perfectly aligned with the corresponding connector on the device.
Also check that there is no dust or dirt on either connector.
If even following these steps still causes the problem, try using a different USB charger.
Some power banks may not be able to recharge the BIKE battery.
This is because the charging current is very low and some power banks may not detect the voltage and may not start charging.
In these cases it will be necessary to use a wall socket or another power bank.