Why Light Maps missing after the Packaging.?

Hi there i have a peculiar problem with the light maps missing some times all of a sudden in the scene and it becomes flat and preview text appears on the mesh.
And its very annoying i am not able o find what might be the reason for loosing this light maps ???

And some times the light maps are missing after the packaging finished when i open the final build its flat no light maps… ??

Can any one help me out to trace the problem.

Hi, if you haven’t found a fix to your issue yet here are a few steps I recommend:

- Delete all old light-map data

- Shut down project and Epic Games Launcher

- Open Swarm Agent and Clean and Validate ( C:/…4.19/engine/binaries/dotNet.SwarmAgent.exe)

- Go to App Data and delete all contents of Unreal Engine (C:\Users\UserName\AppData\Local\UnrealEngine)

- Create a new project

- Open old project and migrate all assets across

- Open up new project, set up project as it was before (should only be project settings, plugins etc)

- Build lights

- Save lighting data