Cowl won’t stay clipped to windshield

After replacing spark plugs in my 2016 Prius 2, I replaced the plastic cowl in the approved manner, snapping the edge into the slot under the windshield and installing the pop pins and end caps. The part snapped positively into the windshield clip all along its edge, and the pin holes lined up. However, every time I drive the car, the cowl pops out of its slot. I can push it back into place with a noticeable snapping sound, and it looks perfectly positioned, but it only stays there for an hour or so.

Any ideas?