I got this bidet from Amazon and I've been trying to install. The instructions tell me to remove the toilet seat cover, place bidet and then attach the seat cover. Fairly simple install. But I cannot, for the life of me, unscrew the toilet seat cover. The screw is plastic and I cannot unscrew it. I tried with a flat screwdriver and it just rotates forever without coming out. I tried pulling it up to "dislodge" it but no dice. There is some kind of putty like material between the seat and the bowl where the screw is. Tried to remove it. Nothing. I am afraid I'd damage the screw. Any suggestions?