kkkkkkabc
1 - It could be that you don't have a physics body for the floor. you do however have a CSG node. In the CSG node you can enable collisionto make it a physics object.
2 - make sure your physics bodies or their parents don't have scale applied. colliders should not be scaled because it causes bugs, but the engine will alert you of this.
3 - if it's none of the above, it could have something to do with player. what IS player? I deduce that you just dragged the blend file into godot and called it a day. that's not how you are supposed to do it, you are supposed to create an inherited scene and save it, then you can clear inheritance and modify it to turn it into a character scene, but your file must be finished for this.