Clips for front turn signal do not snap in, is there a remedy?

Hello, can someone tell me how the VW Lupo flasher hood is fixed sideways between front bumper and bonnet? There are clips, see photos, which supposedly only have to be pressed on and then snapped. But they don’t. Nothing rests, it doesn’t hold anything. Even with the greatest effort they are not locked in, just a bracket for the clips on the aperture has already broken away. (How can you construct such thin bridges where a force effect is necessary?) How should the clips work at all? Do the transparant sleeves remain on the white pins or do they have to be pulled off beforehand and inserted into the holes of the fenders? I have already tried to understand the function, to press the pins into the sleeves with the pliers, but nothing moves at all. I also tried to pull out. Also, zero movement. How should this hold, I can easily push the clips into the fender holes and pull them out again. If the pen is in the sleeve, I should never ask for a solution.