In Unreal Engine Caustics 5.1, how can I operate to see the reflected light spot on the ground when turning on path tracing?

In Unreal Engine Caustics 5.1, how can I operate to see the reflected light spot on the ground when turning on path tracing? Figure 1 shows that I can see the ground light spot using default lighting, but Figure 2 shows that the light spot on the ground disappears when turning on path tracing


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