This may be a silly question, but I'll ask it anyway. I'm not familiar with your AVR, but on the Denon, there is a separate setting to tell the AVR that you have a sub. When you added the sub, did you change the AVR to Sub=Yes?

Check to see if anything is coming out of the sub.

LFR1100 Actives,QS10HPx2,QS8x2,EP800,M3x4,M3x2 (Wood),M5HPx2 (Wood),AxiomAir,ADA1500-8,ADA1500-7