Norman's gym
The gym leader is not at the gym and that is why we cannot enter the gym.
petalaburg city
after the fifth gym in your dad gym, Wally's parents give it to you
you walk there ;) F YOU. that was useless
The Fifth Gym is in Petalburg city....(time to vs your Dad!)
you go to Petelberge city and talk to your dad.
Four gym's you r dad is in the fifth gym.
You go to Fortree City to take on on the flying type gym leader!
You must first get the fifth gym badge then the leader gives it to you.
If you talk to Norman, he says that he will battle you once you can show him four Gym Badges. Therefore, his gym, the Petalburg Gym, is the fifth one that you shall conquer.
It depends on the version. In Pokemon Ruby, Sapphire, and Emerald, the fifth gym leader is Norman. He specializes in using normal type Pokemon and he is your father. His Pokemon are 2 Vigoroth and 1 Slacking.
The fifth gym is at hearthome city