V-Ray Light Gen, in some versions, fails to write temporary HDRI preview files to a path containing a space. It silently fails. No error. Just a dead, dark dome.
They selected the dome, chose "Sunset," and hit . vray light gen not working
Alex’s Windows username was — with a space. V-Ray Light Gen, in some versions, fails to
Twenty minutes later, after sweating through the fix, Alex had a beautiful golden sunset. They delivered on time. But they never forgot: check the damn path spaces. V-Ray Light Gen
The fix? Change the to a simple path like C:\VRayTemp (no spaces). Or, in newer versions, update to the latest hotfix.
Alex thought, "No problem. I'll use V-Ray Light Gen. Click a preset. Done."