Unable to charge the speaker
When using a USB AC adaptor (commercially available), make sure the micro-USB cable is firmly connected to the speaker and the USB AC adaptor. In addition, make sure the USB AC adaptor is firmly connected to an AC outlet.
The speaker supports a USB AC adaptor (commercially available) with an output current of 500 mA or more. However, using a supplied micro-USB cable or micro-USB cable conforming to the USB standard is recommended. Charging from the other device is not guaranteed.
You can also charge the built-in battery by connecting it to a booted computer via the micro-USB cable. However, operation with all computers is not guaranteed. Operation with a home-built computer is also not covered by the warranty.