How do i make my character not fall through the ground

I created a character in maya and imported it into unity. I’m still kind of a newbie at unity. Can someone explain to me why my character falls through the ground despite it having a rigid body and the box having a box collider? And what process i need to make my imported character not fall through the box.

In the inspector, loot at the objects mesh and tick the box named Convex


Make sure the mesh is not clipping the ground in any way
even if it will slightly touch the ground, it will fall through once you start the scene