Do you even have the iEra tileset? FYI: it doesn't automatically come when you install packages for level editor. Are you sure you are not mistaking it for Era PC's tileset?

wait what? You totally messed up your floor/level. You coppied part of your floor over your level. But what you are standing near is not it. Look at the TOP left and top right of your level. there is a corner ceiling tile without a wall tile under it.