Swarm failed to kick off

Hi. My first question.

My project was worked in 4.12 originally.

And few weeks later, 4.13 released.

So, I moved my project 4.12 to 4.13.

While first few days at 4.13, every build was OK.

But, In recent days, the error occur.

When I Click the ‘Build’ or ‘Build Lighting Only’ to build, error message

‘Lighting build faild. Swarm failed to kick off’ is showing.

And absolutely, failing build.

What is problem?

I tried Rebuilding the Lightmass in UE4.sln, Reinstalling the Engine, Fixing additional Plug-in Crash problem.

Help me!