My speaker did this. I was able to fix it by resetting the speaker.
Plug it in, and let it charge for a while, just to make sure it has really does have a charge (like half an hour, minimum).
Then hold down the minus button, and the power button for about twelve seconds, until you get a beep.
That's all it took for the speaker to start up correctly.
After that, I did have to forget the blue tooth device, and reconnect new. I don't know if that is part of the process.