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Unreal hangs and fails to build lighting

Short situation description: We are using Unreal 4.24 to develop a marketing video for a project, but everything is in a closed lab where there is no internet access and a host of security protocols. We built Unreal from the source code and copied it onto a machine, as well as installing the Epic Games Launcher to get all of the DLLs. The PC will never be connected to the internet again, and getting any error logs outside is a whole process. The Epic Launcher is installed, but it won’t open because it wants to check for updates and cannot.

The problem: When I attempt to build lighting, Unreal hangs and stops responding at “Starting Up Swarm Connection: 100%”. It never completes no matter how long I leave it. The lighting is not built. This happens even with an empty scene and the starter content scene. It doesn’t crash or anything particularly helpful. I have not found any other problems with the Editor. I can even render a video, but it still has the “Preview” shadow in the lighting

Tested:

  • Took the version of Unreal that we built, installed it onto another work PC that is connected to the internet, and tested it. The lighting build worked.

  • Disconnected that PC from the internet and built lighting. Still worked.

  • Disconnected the PC in the lab from the lab network (thought that the network might be the problem). Still didn’t work

Swarm did generate a log file, but I categorically cannot bring that out and post publicly. If I can contact support I can email it to them once it’s been cleared but in the meantime, I remember two things from the file.
It complained about “Windows FIPS Validation” and that the Swarm system failed to make a TCP connection and tried to make an ICP connection.

I’m looking for suggestions for ways to debug and at least identify the issue. We have a tight deadline coming up so if I can’t fix this soon we will need to switch to an animation-only software like Maya or something (which I don’t want to do).

I have no idea, but you could just use dynamic lighting…