AGlows uses the geometry of an object to create a light source. It doesn't make the object 'glow' (you need the glow channel of the shader to do that) but it enables your object to shine light on your scene. The problem you're having with the Fire object is that it doesn't have geometry for AGlows to use. The solution is to use a bulb instead, perhaps with a gel to create better 'firelight'. My version uses an orange bulb with a greyscale gel but a colored gel would perhaps look better.