This could be similar to the other issue that was posted with metal turning black recently.
had some issues with it myself when trying to set up a darker than usual metal material - however it worked fine for Gold, so unsure if that has anything to actually do with it.
if you are adding a reflection capture, make sure to rebuild captures and light.
the material itself will essentially reflect, but it isn’t a mirror.
to have an actual mirror like effect you need to enable planar Reflections and set it up for it.
Plenty of tuts on that, but go with the official ones
https://youtu.be/1Sx9qINRoIY