@jupkmn The error message may be misleading here. Try rotating the shower: maybe the issue is that in the direction you're trying to place it, the shower door would be blocked by a wall.
If that doesn't help, remove the wall next to the toilet, place the shower in the orientation you want, then draw the wall again.
@puzzlezaddict There is no door in this case, I can place it rotated, but not on this wall. I tried to remove the wall and put it again, but with no success, I even tried to place on different spots in this wall, but still the same message appears.
@jupkmn I meant the door on the shower itself, as in, the way the sims enter and exit the shower. I was suggesting making sure that shower door pointed away from the three walls.
If that doesn't work, try taking all the other objects out of the bathroom and deleting the wall, then placing the shower and making sure the sims step in and out of it in the direction you want. Rotate as necessary, then add the other objects.
It's also possible that this shower simply needs more room than you're giving it, but I don't know for sure. You could experiment with building on a different lot or trying a different shower, or maybe someone else who's used to building in tight spaces will see this thread and recognize the problem.
@puzzlezaddict I don't know if you saw the images I uploaded, but it is one of those "doorless (?)" showers, but the arrow showing the steps are not being blocked. I tried to delete the whole bathroom and build again, but somehow I'm still not able to put the shower on that specific wall. I also realised that I can't put any doorless showers there, but the closed (?) ones I can.
@jupkmn I did see your earlier screenshots, and I was thinking that maybe the direction of the arrow was deceptive. For example, in your second post, it looks like you could place the shower with the arrow pointing towards the toilet, then perhaps draw the wall afterward. What I couldn't tell is if the arrow actually pointed to the side of the shower where sims would enter and exit—even though it should, that wouldn't be a surprising mistake.
Anyway, if you can't place that shower where you want it in any direction, I think it's safe to assume that the shower doesn't fit in the space you want to use for whatever reason, and you'll need to either use a different shower or redesign the bathroom.
I tested this in a test build and had no problem getting the shower to place in 1x1 tile space in the arrangement I see in your pic. From the angles of your screenshots, I can't see all the walls around the shower though. What I think might be going on is an object of some type may be blocking you. Is there anything other than the shower inside the shower stall like a towel rack or the wall shampoo holder? Showers will block placing other wall mounted objects in close proximity and vice versa. It could be a light or maybe even that light you mounted on the exterior too. Almost anything. And will it place it you delete that short wall? If it does, try putting the wall back after the shower is in place.
One other thing since the error message says it must be on a floor. Are you trying to place it on a platform? That could be the problem if you built the room with a platform rather than a foundation.
If you still can't find anything blocking it or another way to get it to work, then you could try placing it with MOO on and it should go in the orientation you want it to. If it will place then, try sending a sim to take a shower in it and see if there is a route fail. If it works, then you should be good to go.
Hope this helps.
The quick way to check if a house was built on a platform is to try to change the foundation to a different look. Just go to an exterior wall where you can see the foundation and try to change it. You can't change it when the house is built on a platform.
Another way to check is grab the big arrow in the middle of the build and pull the foundation up. If the floor level inside is not even with the top of the foundation, then there's a platform there.
If you remember and can tell me the name and creator of the lot you downloaded, I can download it and check it to see if there is a problem with it.
Edit: I went back and looked at all your pics again. From what I can see, there are definitely platforms in the build. So I think that the platform is probably the cause of your problem. It looks like there is a platform in the room behind the bathroom. I can't tell if the bathroom is on one though but I think probably not. But since the shower will place on the other walls and not on the one that has a platform on the other side, it is because platforms intrude into a wall. There are a lot of objects that won't place against a platform and that shower is probably one of them since the open showers also intrude into the wall. So you're going to have to use MOO to place it in the position you want it. It should work just fine though.
Hope this helps.
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