I took that part off and put it back in quite a few times. It's hard to make it stay put. Unless something is broken, you can line up the clips with the holes and use your hand as a hammer to hammer it back in by the clips.
I didn't notice anything specific broken... but the clips has these black rubber gunk thing that's kinda glued onto it. I think maybe it used to be something that was attached to the end of the clip that help keeps it in place thats gone now.
I might be talking out of my butt, but when I removed mine earlier in the week for the footwell mod, there were 4 clips in the front and 2 points in the back that held it taught. Are the two points in the rear still there?