I’ve just found this in the docs:
Note: when enabling SSS do not use the first light in the Light palette as this will not work; choose any of the other seven lights. The light does not need to be turned on, simply have its SSS button turned on.
I (foolishly) assumed that all lights were the same but with different settings which could be changed so they are all similiar (effectively) Are there any other properties with the lights that a newcomer should be aware of?
Cheers