Hey first of all I am from Belgium so I apologise for my English.
If your speaker turns on when you charge it ,but not when you push the power button if you don't charge it.
The only thing you have to do is charge it and if your speaker turns on hold the power button and the volume minus - button simultaneously until it turns off.
Than pull out the cable and push the power button.
If it doesn't turns on you should repeat the previous steps but instead of pushing the power button and the volume minus button press the power button and the volume plus button until it turns of.