I’ve had the same issue now with 2 different Soundcore Boosts and it occurs no matter what cable or method of charging is used.
When kept plugged in all the time it will work for a day or two, however after a few days the speaker will turn on but not play any sound (neither the power up sound or any music streamed from your device). If you then unplug the Soundcore Boost, it turns off immediately. Upon plugging it back in it starts charging again showing 1 LED.
There seems to be a big flaw in this speaker that it is not able to be kept plugged in constantly and used while charging.