Concave Mesh Collider with Ridgedbody problem

I'm using unity 2019.4.1f1 and I'm having a problem with colliders. I have a box with an opening I have my view mesh and my collider mesh. I select my collider mesh in the Mesh collider and then add a rigidbody to it. when I test it, it falls right though the ground. When I disable gravity it floats and I cannot touch it. If I enable convex all the physics works but it's not concave and the opening is useless. If I check is Kinematic or remove the rigidbody altogether the collider works properly but doesn't of course fall from gravity and remains locked in place in mid air. I'm probably dumb or overlooking something but I never had this problem before in unity 2017 release.