Newbie in trouble, cleaned ac filter cover won’t go back on

91 26’ terry resort. Kinda new to having a camper saw the ac filters were dirty removed my knobs, 2 screws slid cover off... cleaned. Put back together and the back side opposite the knobs is not flush on ceiling... like enough for me to stick my fingers in. It feels stuck but for the life of me there is nothing. Tried a couple snacks, wigging, taking off putting back. Nothing. Screw holes line up but the back is gapped. Can provide pics.