Steps to repro:
1. Create a new project
2. Add a cube to it and make it static
3. Now create a material with metallic and smoothness to 1 and apply to the cube
4. Open lighting panel, uncheck auto and click on bake

Note that everything is fine at this point

5. Clear the baked data

Cube is rendered completely black

Now create new material assets with reflection and smoothness as 1 and note that its completely black as well (the material asset itself is black)

Baking again, would fix the material assets as well.