Thanks @doris4jin and @elmo41683 for the help!
They are correct:
- When not charging other devices:
the button will show you how much power is remaining in the power bank (so you know if you need to charge it before a trip, for example).
- When charging:
the LEDs will always be on because the power bank is "on" anyways to charge your device and the LEDs themselves use a negligible amount of power.
@middleanchor, it's possible the LEDs were off when you connected your device, but in that case, your device was likely not charging. Pressing the power button will "wake up" the power bank, turn on the LEDs and start the charging process. I hope this helps!