I think I might know your problem. When you add a tile which format/style is the tileset looking like.
The First one is the format Era uses and is used for "addtiledef" scripts. The one classic uses is "addtiledef2". So if your using the tileset Era is using. It'll probably look like this.
NPC Code:
//NPC made by Unknown
//Tiles
if (created && playerenters) {addtiledef tileset_name.ext,#L,0;}
Replace tileset_name.ext to a similar tileset for example. "tileset_era-summer.png"
#L is current level, and 0 is the mode of the addtiledef which in case Era is
using. If it's still not working than switch the 0 to 1. That should help, PM me if it doesn't work.
I prefer using the tileset type Era is using because it's easy to script with. Addtiledef2 requires the x,y coordinates
and I suck at those.