None of the NPCs you have like the Snow biome or who they are living with so they aren’t going to give you the Pylon. Try pairing the Mechanic with the Goblin Tinkerer, they are basically guaranteed to give you the almost any Pylon when paired together. If you are missing one of those two you can look at the
list of living preferences on the Wiki to find a different pair.
Yes, but the mechanic + goblin tinkerer is only available post skeletron
Merchant + Nurse + Golfer also can give you pretty much all pylons, and it's available pre-bosses.
edit: never mind. what I said is true, but is OP in mid-hardmode?
since there's a true night's edge, pickaxe axe, etc.
I was just confused that most NPCs are not present who normally should moved in long ago (but either there's no free housing, or they're temporarily all dead due to a recent pirate invasion or such maybe)