If they're plugged into the wrong spots, the unit can behave very weird. I would definitely at least verify that they're in the right spot. I had a kit version, and the instructions for the RJ11 wires didn't work out for me, they were in the wrong spots. I ended up having to follow the leads on the board itself, mainly using
this image to figure out which one went where. I think it had something to do with using a weird standard RJ11 cable, so the colors were backwards.
Since it's the pre-assembled version, we can probably rule out anything being shorted out, but it wouldn't hurt to take a look at the unit and make sure that none of the metal leads are touching anything else on another part of the board.