1999 Nissan Maxima Cabin filter replacement

I have recently tried to replace cabin filter with no success. I have glove box off and could swear I have all the screws out and clip off, but can only get bottom to move down about an inch. Can see filter and its very dirty don't think it has every been changed. Can you please help and let me know what I am doing wrong. Is there another screw I can't see or a clip under the hood. I can get whole case to move but can't get it to open. Thanks for any help