Let's be scientific a bit if I may.

You say your shader works *under your very specifically set up lighting with render settings you have*.

You changed a variable i.e. the lights for a scene that is different.

The shader on your figure presented with those black blotches.

You asked why.

Very knowledgeable people offered suggestions here (I just dabble, not referring to myself). Very clear suggestions were made why your shader behaves the way it is, what specific nodes are not working or unnecessary, and suggested what you can try.

As was pointed out above, just because a construct works under one specific circumstance does not mean it is viable. As soon as you change one variable, it ceases to work--meaning you can only ever use it one specific way. That, for me, kills the joy of doing art (to go back from science to art a bit).

The way light reflects on a surface, the way changing that light changes that reflection, is, on our computers, becomes science again with the help of nodes, back from mystery--the more advanced the software we use becomes, the simpler it seems to be. Keeping up with those changes as Poser, in our case, is developed, is not easy and I still struggle with the way Superfly evolves and changes--in most of the cases, delightfully simplifying the way we do renders now.

I think it's a super valuable thing to have explained and dissected on these forums, and worth trying and working with.

Good luck with whatever you decide to you and thanks for all who shared their thoughts.