That was it.
Alex thought, "No problem. I'll use V-Ray Light Gen. Click a preset. Done." vray light gen not working
It was 2 AM. Alex had a villa exterior due in 12 hours. The client wanted "dramatic, cinematic sunset lighting." That was it
They restarted 3ds Max. Reset the scene. Tried "Morning." Same thing. The dome light stayed stubbornly black. Click a preset
The little progress bar appeared... crawled to 100%... and then… nothing. The Light Gen window went blank. The dome light in the viewport was still dark. No textures. No preview. Just silence.
The fix? Change the to a simple path like C:\VRayTemp (no spaces). Or, in newer versions, update to the latest hotfix.
They Googled furiously: "vray light gen not working" — and found forum threads from 2018, vague mentions of "paths," and a buried comment about "Windows usernames with spaces."