No audio from sub

Hey, I've got myself a 12 inch fli sub along with a 4-way jbl a6004 amplifier
Head unit is a Sony wx800bt
Car is an Opel Corsa C 2006 (If that matters)

I have the main power connected from the battery to the amp
I've got the remote connected from my head unit to the amp
I've got the 2 rca cables plugged into the sub output on the heat unit
And then I've got the ground hooked up to a big solid bolt under my back seat

And now the plan is to use this amplifier only for the one subwoofer.
I connected the rca cables from the head unit to the CH1 and CH2 rca ports on the amp
And then i connected the 2 cables from the amp to the subwoofer in from CH1 (+ & -)

The amp turns on and off fine when the ignition is on and off, and my side door speakers work as always, but no sound comes out from the sub.

Can anyone tell me what I'm doing wrong, the reason I'm not hooking any speakers to the amp is because I don't have enough wires to hook them up to the amp. This is also my first time setting up a subwoofer, I found a nice deal on the sub + amp and I couldn't say no to that

Any help appreciated, All parts are brand new, so they're unlikely to be faulty