Get down in the passenger footwell. Work the temperature slider & look for a couple levers moving. Forward of the stereo, I think you can see them if you put your head way down there like you're trying to see the back of the stereo.
Then go out & open the hood. Look for the heater valve on one of the hoses sorta below the fuel filter. Check whether the cable is disconnected or broken out there. On that website, that 2nd cable is shown in the picture of the heater unit, or maybe the heater hoses.