Falling through all my floors help D:

[Metarurufu]

I'm new to the level editor and I've been using it for a week or so now,no problems.I never had the problem before,but all of a sudden every time I load my map in amnesia I fall through the floor.The floor isn't even there,I'm making an outdoor map.When I spawn there isn't ground,it's set to collide ,but still nothing.Please help me,it's really frustrating that I can't test my work.