You will have to put the ladder 1z down (or was it up?) inside these multis.
Also possible is that some floor tile on the first floor is blocking you from walking upstairs. That's hard to see on this picture.
I asume that this is a multi?
If so, do you have a .wsc file or something else like that of that single multi or can you give a link to the multi.mul/idx which contains that building? Then i test it on our shard.
On the first floor i can walk without problems.
On the ground floor i also can't walk into or in that room.
This is because there are a lot of invisible slate roofs (Objtype: 0x59f = 1439) filling the whole room