3rd Gen New Mauville

[Palamon]

This is an area in Hoenn that has a small sidequest for you to do. After getting the fifth badge (gen 3) or capturing or defeating the box legendary (or/as), Wattson will ask you to go turn off the generator there. Once this is done, Wattson will give you TM24, Thunderbolt. Nosepass and Magneton can also evolve here.

The original version of New Mauville has a puzzle to figure out as well. This area is also the only place where you can catch Magnemite and Voltorb in the Hoenn region.

Did you do the New Mauville sidequest? I always do it, as I feel like it's required.

 

[Lysander]

I usually do the New Mauville quest whenever I play any of the Hoenn games, at least at some point. Definitely worth doing it to get the Thunderbolt TM, especially since its the only way to it ORAS (In RSE you can buy it from the Game Corner as well)

 

[XNaut]

I always did the New Mauville sidequest and I don't think you're allowed to even get further in the game without completing the quest. I don't remember but I could have sworn completing the New Mauville sidequest opens up a new path to get to the next gym.

 

[Lysander]

I'm pretty sure you don't need to do this sidequest to get through the game. The path to the 6th Gym is unlocked by being able to use Surf after beating the 5th Gym.

 

[Venonat in Space]

Definitely not required in the sixth gen ORAS just saying. I've done the challenge in ORAS multiple times on different playthroughs. As for third gen, I don't recall doing it on the super old Emerald cartridge I have. Then again, I never restarted since it's my brother's game on there and has his name, and I just thought, eh...for the legacy. So...idk.

EDIT: On the Emerald cartridge, all I ever done on it was catch more 'mons just so you know...