Hooking up Jbl hti 88 with denon dvr 486
I have a denon dvr 486 receiver and 4 boston acoustics 460 and dsi 453 as center and 2 vri 553 in the ceiling and am using a JBL HTI 88 for the sub. I have the sub hooked up to the left and right front channels with the right and left fronts hooked up through the subwoofer. It seems that the sub is not getting power. Can anyone suggest what the problem is and a solution, which recognizes that it has already been wired in the walls so a solution that would not require cutting more holes in the walls?
Thank you in advance