Why wont my subs hit?

ok so i am super confused. my amp powers on and lights up and **** and my subs are definately hooked up to the amp, because #1 when you touch the speaker wire to the imputs on the amp the subs pulse if you will, and #2 when i flip the amp from lpf to hpf the right sub pulses. and i have all the nobs turned right on the amp because i did gett the subs to work the other day for about a day by somehow switchin the amp from lpf to hpf a bunch of times and it sounded great. but now it just wont work at all..... so i have no idea... hope you guys can help me figure it out