davidfre21 is right. if you follow the directions on the replacement mirror glue it will hold. be sure to follow directions spot on spot though or it won't work. kinda surprised gorilla glue didn't work. did you clean the window with rubbing alcohol and wet one of the surfaces when using the gorilla?
i got mine to stay on with the rear view mirror glue from autozone. i filed the metal mount to be flat and sanded with some 36 grit sand paper. used the glue exactly how it's directed. i could do pull ups on it if the window wouldn't break.
i used to have the problem in my old maxima....i took a piece of hemp from a broken necklace and wrapped it tightly around the joint of where the mirror meets the arm that hold its......if ur mirror is just falling off the winshield......find an adhesive made specifically for glass, i think liquid nails makes one.....not sure if u used that or regular liquid nails......