Probably not an issue. It’s likely that the lowest level is just a bit too weak to properly power the LED. IIRC, you can change the moonlight levels in Narsil, from something like 1 to 7. I think the lowest selectable level almost never works. The default is 3, I think. Try setting it to level 4 and see if that helps. Look at the very confusing Narsil guide for details.