LEGO Set 10188 Help on Step 160
I'd double check that you've got all 16 links in the chain - if you're trying to squeeze it into a circle with less than that it won't fit. Also double check the placement of the pieces from sub-steps 7 and 8.

Finally, when forming the circle, try carefully working your way around from one end, moving completing each bracket before moving on to the next - possible starting with just one click each, and then going back and adding another as needed.