I created this part and rendered it without applying any material and it has the appearance of aluminum.

Then I applied Chroma material to the part to obtain a better result of the metallic appearance like a mirror but the part became darker, though I increased the lights.

I eventually found out the problem is relative to the properties of the material but when I referred to the properties of the chrome, I saw all its options were inactive. What is the cause and how I can active them?