Look for the lines SetAmbientLight in the script of my map "Runes in Good Hands," it worked for me.
It's strange, I'm doing it the same way as you, but nothing happens, and the console is still silent. I really don't know what to think :o Even a simple SetAmbientLight outside the trigger doesn't change anything. I'll have to try it on a separate map, maybe I messed something up there). In any case, thank you very much for the advice!