I beat the pokemon leauge(1 time) and the guy still won't let me passed! how do i get passed him (LGFR)????
beat the 2nd elite 4 after finishing the 7 isle mission (finding both ruby and sapphire)
>An Ace Trainer guards the mouth of the cave and only allows powerful Trainers who own all eight Gym badges and have competed in and won the Pokémon League beating the Elite Four to enter its premises.
>... Another addition in FireRed and LeafGreen lies in the fact that Trainers are now required to further prove themselves before entering the cave,
which is done by completing the quest on Sevii Islands and restoring the Network Machine to operational status.
Source: Bulbapedia/ Cerulean Cave