keep going, it takes quite a long time to tighten up. if it doesnt tighten at all, like i said you may have a very wide steerer tube, or the little nut at the top of the allen bolt is not sitting in the nut shaped recess properly. try it with the bracket outside the bike frame. as you tighten the allen bolt, the nut on the top should pull the two plastic blocks together and spread them wider.