Lightmaps not appearing on large static mesh

Unreal light baking issue. On a large mesh I processed in Houdini to create texture atlas then imported as FBX in Unreal.
In Unreal placed in level, set mobility to Static, but after a light bake none of my light maps are showing up.
Could this have something to do with the Source And Destination Lightmap Indexes in the Static Mesh Editor? Right now they are 0 and 1 respectively.

If not what else could be the cause?

FWIW It was a lightmass importance volume in my scene set way too small. Should have an infinite extent toggle like the PPV.