I set up the cobbler to run a simple temperature sensor circuit - a 4.7K and DS18B20 using (3.3V, GND, p04). Didn’t work - the DS18B20 just didn’t show up. Run directly off the Pi pins, no probs. Tried an LED circuit off the same pins (3.3V, GND, p04) LED lit when it should, went off when it should. So why the cobbler work for one component and not another? Is it just a defective cobbler or what? Weird, huh?
It could possibly be a dodgy solder joint- have a close look at the soldering on the Cobbler and see if either of the joints required for P04 are a little dry or shy of solder.
In addition to what @gadgetoid said please feel free to take a photo of the solder joints and post it here for us to take a look at!