When your Echo Alexa does not turn on and respond to tour voice command then you need to recheck some essential things first:
ü Check that the power adapter is properly plugged in or not
ü Power cables are not damaged and faulty
ü Verify that the power switch is turned on or not
If all these are working fine then there may be some other serious issue which can be diagnosed and fixed easily by dialing Echo Alexa customer support number 1-800-234-6190 available 24x7.