My Lighting isn't getting built, why?

well while building my scene it showed a warning saying***“InstancedFoliageActor_0 The total lightmap size for this InstancedStaticMeshComponent is large, consider reducing the component’s lightmap resolution or number of mesh instances in this component”*** I did what it said and I lowered them to the lowest possible lightmap resolution, but still its showing that error and the lighting isn’t getting at all, Please help!