Благодарю премного!!! Вопрос закрыт.
https://coronarenderer.freshdesk.com/support/solutions/articles/12000017218-how-to-use-interactive-lightmix-
"Using the ShadowCatcher materialLightMix does not interactively update shadow catcher material shading results - this is currently a limitation.Solution: use the >Scene button to bake LightMix properties into the scene. Then re-render your image and use the beauty pass to get the correct ShadowCatcher result. "
1.6 и конверт настроек лайтмикса в настройки света в сцене )