So this human mesh always falls through the ground in my game!!! I put character physics on it so it falls, but it always go's through the floor. I tried to have it land on a skateboard when the game starts, but the skateboard just slips away and they both fall. Why is this? there are character physics on the skateboard too. Check the image This is the human before falling through completely Also sometimes it won't even fall to the floor and will just shake and hover above the ground as well as the skateboard. why will they either fall through or not even touch?
Two things, firstly, make sure that you also have Collision physics on the plane. The character needs physics, but the plane does, too.
Secondly, your character is intersecting the floor plane. When the physics simulation starts in this kind of situation, it doesn't have any way to decide which side of the plane the character is on, so it freaks out instead.
Re-position your character model so that he's entirely above the plane before the simulation starts.
Vili's suggestion to apply rotation and scale is also a good idea.