Object falls through floor

Hi, I can't seem to find the answer to this. I have made a random object in Blender, and imported it. I gave it a Rigid Body and a Mesh Collider, and it falls through the floor when I play the game. The ground has a Terrain Collider (It's a terrain), and nothing else falls through the ground. What's going on here? Thanks!

set the mesh collider to convex