Snow Pylon in Legendary Mode

[Frak]

hello i am playing on legendary mode and i wanted to set up a snow pylon to access the aether biome but my NPCs won't sell any pylons, im not sure why. i have 1500+ snow blocks in the area and the clothier is selling the beanie so it's definitely in the snow biome. the houses are at ~7375' West and ~329' Underground on a large world. any ideas?
screenies and world file below.