Why the subwoofer doesn't work after standby or power-off? The logo-icon on top-panel is not lit even when power cable plugged in??

The subwoofer (Stank/Stank-Turbo) might be in low-power consumption mode when the system is powered off or standby to save energy. And it also might enter deep sleep mode after a long time no use.

Please try to wake it up by pairing it again, sometimes it takes 3-5 times pair-trying to re-activate the subwoofer from deep sleep mode.

Notes: Make sure the system is in the default frequency when you apply this operation. If you are not sure, just try to restore the default frequency in the frequency interface. 

Change/restore system frequency, check this link: 
http://www.starloop.eu/center-faq/10