Can some experts please help me.
My mirror reflections; flooring always shows big patches of solid white.
Please help 
Ultra Setting
|Mirror Roughness 0% Metalic 100%|
|Flooring Roughness 0%|
Are you using an RTX GPU? Enscape using SSR so this could be the limit.
Also see: Why are some of my objects/parts of my project not displayed in reflections?