Why Lights Might Not Appear
The wrong mod loader, a mismatched Minecraft build, or an unsupported item is a more likely starting point than a broken installation.
Check the Basics
Verify the mod appears in the installed-mod list, use the matching game version, and test a known luminous item in a simple world.
Understand Block Limitations
The author describes lighting limitations in foliage, cobwebs, and some incomplete water blocks. Test on open terrain before troubleshooting a specific cave.
Fix Loader Conflicts
Disable other lighting and shader modifications for a clean test; add them back one at a time if the effect returns.
Download and compatibility reference
The Dynamic Lights author project page lists Forge and NeoForge files. The release file list is the best place to confirm exact compatibility. A direct file link is available from the homepage download section.