I presume you are talking about the lexan windstop b/w the roll bars? If so, common issue. First thing, make sure it's latched in all the way and the clips on the side are not broken. If they are all ok, check out the various solutions by doing a forum search.
Here are the results when searching on
Windstop Rattle
I'm sure one of the solutions in these various threads will work for you
