4.13.1 Lightmass Error

I’m just starting out so go easy on me. I built the source files in VB, load a test project with sample materials and attempt to build.

I get the error message:

Light Build Failed. Swarm Failed to Kickoff.

What does this mean?

Is this a known issue with 4.13.1? Do I rebuild, or do I download the newest release and try a rebuild, or do I edit a file or … where do I go from here?

I figured this out. When building from source you have to individually build extra programs. I opened up UE4 and rebuild lightmass.