Those corner caps can be a pain! Did you just push it back down to secure it? I actually just gave up and ordered a new one for my passenger side for $23 or so and the new one is quiet for now. Hopefully I installed it correctly. I found it easiest to slide the long skinny part up and into the windshield/A-pillar groove first and then snap into the cowl. Is that how you did it or is there a better way? I also trimmed or shaved slightly the front clip (that clips to the cowl) to get my driver’s side to snap to the cowl more securely.
My Dealer ordered two new pieces for me in the Fall. I had no issue for a few months. The noise it back. I have an appointment at the dealer in a few weeks. Going to see what they do this time to fix it.