If your Alliance character has not unlocked Mechagon Island, you will get a different quest from a different NPC. Gila Crosswires will have the “Fame Waits For Gnome One” quest which will start them on the island unlock, then they can do the recruitment quest.
https://us.forums.blizzard.com/en/wow/t/clarifying-the-process-for-unlocking-mechagnomes/410713