You might be.

In the main GIJoe pop-up control window, under HDRI Fake, there is a checkbox. That needs to be on in order for your color image to be evaluated/calculated/faked as a HDRI image to achive those cool highlights and reflections that you need

Here is an image for you to see what I mean:

Arrow 1 when this box is checked, you can put your mouse over almost any piece of text in the GIJoe panel, and get help on what it is/does.
Arrow 2 You said you added a color image in this color slot, so I won't talk about that
Arrow 3 when you add a color image to the color slot (see Arrow 2 ), in order for the HDRI effects to happen, this checkbox needs to be checked.



Hope this has helped a little