There are 4 wires going to the amp, well 5 actually.

-The 12v constant, which is a heavy gauge waire directly to the battery with a fuse in between.

-The ground.

-The remote line going to the HU

-The two RCA cables in input, going to the back of the HU.

Post 14 says the amp powers up, so it's probably safe to look between the amp and the subs. There's no wire listed for that above, but post 14 says a thick wire, so I'll assume you didn't overlook getting a signal to the subs.

Do you have the correct crossover selected on the amp? I assume you'd want low pass since you're going to the subs. You may want to adjust the cutoff, or try a different crossover to see if the subs respond.