It’s very very likely your ground doesn’t have collision geometry.
We can’t tell from looking at the screen shot – you need to turn on the collision visualizer.
In general, know that there are two kinds of collision used in Unreal: “Simple” collision, which is used for physics simulation, and “complex” collision, used when more exact representation is needed (such as raycasts for visibility or projectiles.)
If your object doesn’t have too many triangles, you can check the “use complex for simple” box to make the actual object geometry be the physical collision, but this can have severe performance problems if you use it on the wrong object.
For more information, see here: Setting Up Collisions With Static Meshes in Unreal Engine | Unreal Engine 5.1 Documentation