The sound bar has a Stand-by mode feature which auto-powers off after 15- minutes of no signal from the input source.  Below are the different ways to wake up the sound bar:

• If the sound bar went in standby mode because of inactivity for given period, simply press the power button to bring the speaker back online. 
• If the sound bar went in standby mode because of power surge or power cut, simply press the power button to bring the speaker back online. 
• If the red light on the sound is not blinking and the orange/white optical light is solid, please try increasing the volume of the sound bar. If this doesn’t work, try switching source and returning to the original source. This should solve the issue.