On the planner it is not possible to place floortiles on certain edges of the map where they CAN actually be placed in the game. The same goes for areas where you can move away stuff like the greenhouse and the shipping box, and the general grass areas around the farmhouse. The areas that I marked in red on this screenshot have been tested in both game and planner for placability.
You can temporarily disable the restriction check in Options to place tiles whereever you want. Obviously that doesn't keep you then from placing actually impossible tiles
On the planner it is not possible to place floortiles on certain edges of the map where they CAN actually be placed in the game. The same goes for areas where you can move away stuff like the greenhouse and the shipping box, and the general grass areas around the farmhouse. The areas that I marked in red on this screenshot have been tested in both game and planner for placability.
https://i.imgur.com/orwRCZB.png