So currently there’s 2 ways to make enter-able workshop models:
Method 1: Completely Disable collision on the model and add canvas walls
1. Put the model down in the condo
2. Right click the model and select “Disable Collision”
3. Add (invisible) canvas walls to mimic walls and floor. Blocking paths and allowing players to walk around in it.
Method 2: Separate the walls and floors into separate object groups in Blender
If the workshop model is a single object group, then Tower Unite will generate a square’ish collision box around the model.
(For example, you created a box which Tower Unite thinks it’s filled, which is why it is not enter-able.)
However you can separate the walls into separate object groups (while keeping in the same .blend file so the model stays in 1 piece) which will tell the game to change the collision.
(For example, you created a 6 walls positioned to form a box. But the game only sees the walls and not the box, making it enter-able.)
More information on enter able workshop models how to separate groups in blender
Thread: Enter-able building models in workshop?