You have to "click" if you will ALL (7 total I believe) of the clips so the grill will come off. Only then can you reset each of the clips so you can snap the grill back in securely. Unfortunately, it may be extremely difficult to reset the clip on just a couple of them while the grill is still in place.
It's been a very long time ago that I've done this doing the clear corners mod so I may be a little off with the whole process.
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