If you are tightening down the bolts as you put them on, stop. What I typically run into is that if you put on one bolt, get maybe one or two turns in, then put a bolt on the opposing side, leave it very loose again, and keep repeating this pattern that once the chainring bolts are all in place, the chainring slides on. Otherwise, I typically run into the problem you describe. I then tighten in a cross pattern. Worked for me on quite a few different crank/chainring combos.