Worked in a quick test here - you don’t have visibility in reflections turned off for the LightMtl? No Directionality value for the LightMtl? (though the latter would make it appear black / dark rather than just not there, I think).
Sometimes you can’t see the wood for the trees, and that is just when the community comes in to help Had the same thing way back when I was a programmer, just going and talking to someone else was great for solving something that seemed like a complete puzzle. Glad you got it working!