Looks to me like the “reflection” you’re seeing in the material preview one is from the environment texture, not the room itself. Easiest thing to test the cycles version… if you put a light in front of it, is it reflecting the light? If that’s the case, then at the current camera angle, it’s just not picking up enough light from the environment to reflect anything.
From what I’m testing on a simlar scene I have, that value should work, so if you were to put a light source directly in front of the TV, you should be able to see it reflect back.
