One of two things, or even both. NPCs do take time to spawn and can only do during the day. As long as there is an acceptable house and no others waiting then its only a matter of time. The other is to check that what ever you built meets the requirements for a NPC to spawn.
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Techhunter_Talon
Chisaki
@Techhunter_Talon I have, theres a spare room available on a build I have, no ones in it. I checked if it was usable by the NPC. it is :o ;-; it's been days. maybe the arms dealer doesn't like me? xD
Techhunter_Talon
Is the gun in your inventory?