No worries! Whenever you have a reflective surface like metal/shiny plastic, UE4 needs a bit of help to show the reflections via SSR or Reflection Capture actors. Usually SSR works okay in most cases but it doesn’t in your scene, so it doesn’t know what to reflect hence the blackness.
Reflection capture actors do not change any of the values in your materials. You just need to place them where necessary 
https://docs.unrealengine.com/latest/INT/Engine/Rendering/LightingAndShadows/ReflectionEnvironment/index.html
https://docs.unrealengine.com/latest/INT/Resources/ContentExamples/Reflections/1_4/index.html