How is the line going to the filler sealed? Is it a fuel dot? Easy fueler? I seriously doubt the tank position would prevent it from starting, but the centerline of the carb should be aligned with the center of the tank or pretty close to prevent problems during flight. If you close the carb down to a high idle and put your finger over the carb while turning the prop (WTHOUT glow starter attached!), it should draw fuel into the carb fine.

Are you using an electric starter or chicken stick? Has the engine been broken in yet?