Can´t build light on my project anymore Error: System.IO.IOException

Hi everyone. I recently have finished my Archviz project that I´ve been working on for a long time and I´m beyond desperation because I can´t bake light anymore. The house rooms are divided into levels and I started running into issues when I tried Luoshuang´s GPULightmass, before that everything was fine apart from some minor issues. I wasn´t happy at all with the result from GPU baking so I verified the Engine trought the launcher which reverted the changes I did to the Lightmass ini file. I went on my project and rebaked using the production settings, this comes up everytime:

What I´ve done so far in order to fix the project:

  • Reinstall the engine from scratch, about 5 times
  • Migrate the project
  • Build lighting on each level I have separately
  • Reinstalled windows

All of the above has been taking me about 4 days testing and no luck so far, I´ve spent two years on this project, now it´s finish and I can´t deliver it. Situations like this really make me think to check out Unity because is not the first time this happens with the Engine, can anyone help please?

Come on guys, almost two days and NO ONE had this issue? Am I the only one?

After folllowing some internet advice, now the swarm agent crashes on build and this is what comes up:

13:09:07: Starting up SwarmAgent …
13:09:07: … registering SwarmAgent with remoting service
13:09:07: … registering SwarmAgent network channels
13:09:07: … initializing SwarmAgent
13:09:07: … certificate check has failed
13:09:07: … initializing cache
13:09:07: … using cache folder ‘C:/Users/Mac/AppData/Local/UnrealEngine/4.23/Saved/Swarm\SwarmCache’
13:09:07: … recreating SwarmAgent cache staging area
13:09:07: … initializing connection to SwarmCoordinator
13:09:07: … using SwarmCoordinator on RENDER-01
13:09:10: … SwarmCoordinator failed to be initialized
13:09:10: … initializing local performance monitoring subsystem
13:09:14: … initialization successful, SwarmAgent now running
13:09:14: [Interface:TryOpenConnection] Local connection established
13:09:14: [Job] Accepted Job BE4CC6A8-477E2616-468E01B6-1D3634FC

Then I open the Epic Launcher and PROJECT FILES NOT ASSOCIATED fix message comes up, seriously… WTF is going on with Unreal Engine???

I´m really desperate here is anyone who can help me please?

Thanks to everyone that have helped me with this issue, you guys have been really helpful. I´d like to specially thank the Epic Evangelists team, their word made me see the light and all issues were fixed, such a great great professionals.

To anyone out there that has this issue in the future and don´t want to wait for anyone to show up and give you some ideas, I´ll give you some as you will feel as alone as I did:

  • Don´t do any of the stupid steps I´ve specified I did, nothing is going to work no matter what you do.
  • Migrate the level where you have everything (or levels) to another project
  • In my case I´ve had the rooms of the houses separated into levels, so start building light from separated levels, saving constantly.
  • By doing so I´ve realised when I was trying to build light after imported the whole kitchen, thoses errors appeared on the swarm agent
  • It turned out one blueprint that contained my electric appliances was duplicated, same place so visually impossible to distinguish with all assets in between.
  • Same with bathroom and bedroom levels, one static mesh of blueprint containing static meshes was duplicated.
  • The duplicate wasn´t my doing, it was Unreal´s bug while building light for 3 days straight and crashing at 99%. I tried to push my CPU too much and I paid the consequences.

One lesson I´ve learned is that you really need to do back ups, get an external drive, cloud, whatever but do back ups of your work. Don´t get me wrong I had two backups of my work but those were 10 days old and the ammount of work I put between those 10 days was quite considerably to just toss it out and use the old one, but I should have done a backup of what Initially I was happy with, I just wanted to push forward the engine and get better results, never again.

What I also noticed is Unreal still has a lot of work to do to integrate better with Datasmith. Since it´s release I have been using the Datasmith plugin on a daily basis, but if for any reason you move or change name or simply migrate your project to another one, Unreal might have issues with some Static Meshes, not all but with some, for some random explanation that I can´t understand.