How come I cannot stand on a ground?

I am a rookie in Unreal Engine. I just imported a scene from 3ds max and I found my third person character cannot stand on the ground. I checked the details of the ground that ‘Yes’ was chosen for ‘Can Character Step Up On’. How can I solve it?

Make sure your ground mesh has collisions enabled or maybe sometimes you have to go to Build → Rebuild paths

In the details panel, I clicked ‘Simulation Generates Hit Events’ under Collision. And also click ‘Build’ at the top tool bar. But when I press ‘Play’, my character still can’t stand on the mesh…

Oh! I know what you mean and find out what’s going wrong now. Thanks!