Wiring a dual telephone jack?

I have a dual telephone jack in one of my bedrooms that wasn't working. I got one jack working, but not both of them.

There are two main telephone lines coming into the box (each one containing the black, yellow, green, red wires). I connected the wires from one main line into the top jack, and the wires from the other main line into the bottom jack, hooking them up color coordinated. The top jack works, but the bottom jack doesn't. Is there any special wiring involved for a dual jack to get both of them working? There is only one active line in our house, if that matters.

The way they were wired before was completely wrong, and I suspect that's why neither one was working before. I've checked all of the other jacks in the house, and found that a few weren't working, but I've already fixed that problem (there was a loose wire in one of the jacks, causing some of them to not work).

I made sure the wires were tight, touching, etc. so that isn't a problem as far as I can tell.

 

You sound absolutely sure that you have the correct wires to both jacks.

The only other possibilities are: the wires between the jacks are broken, or you have a bad jack.