Onkyo SKW-558 subwoofer no sound

My Onkyo subwoofer SKW558 does not have any sound. When I remove the Pre out RCA cable sometimes the blue light is on. I tried to connect the subwoofer to another amplifier and as soon as I plug in the RCA cable the blue light goes off. I tried connecting the pre out of my only HT-R558 to another normal subwoofer and the sound appears. So the issue is with my skw 558 subwoofer. Will anyone please help me what to do. Is there a way to disable the power efficiency mode in subwoofer?
Thanks in advance.