This error message occurs when there is a Normal Bump map present in the scene. As 3ds Max’s native Normal Bump map is insufficient and sometimes problematic, Corona employs it’s own normal map - CoronaNormal. It’s highly recommended to use CoronaNormal map only.
Solutions:
Replace Normal Bump map with CoronaNormal map. This can be easily automated for large scenes with multiple materials using the Converter Script.
See: How to use normal maps?