I can't remember if the Rebel G (which is the one I have stored away in a draw somewhere) had to have a lens on to work and if the contacts between the lens and camera weren't clean and seated right that it wouldn't fire. It may not have had this requirement although my later Canon's did.
I can't remember any other special settings that it did before it would turn on. You might check that the contacts inside the camera for the battery are clean.
The Rebel G was my first automatic, auto focus camera, and I fought with it for a long time with focus. I kept wanting to manual focus it and the lens was just not designed to be manually focused... the focus ring was too small and in the wrong place. After I finally was able to over come years and years of controlling my own destiny with a camera (mainly the RB67 that I used for years), I had better luck with it. The auto focus still wasn't that great until I moved up to the EOS 3 (which is also in a draw somewhere).
Mike