Mask off the subject and only work on the background
Brightness/Contrast... and fiddle... or Exposure - Try messing with Gamma... or just mess with everything![]()
Brightness/Contrast... and fiddle... or Exposure - Try messing with Gamma... or just mess with everything![]()

I think a major question is, was it white to begin with (i.e. in real life)? If so then your white-balance is off.
Not necessarily, as dependant on the lighting you can turn a white wall completely black.
If it had a blue or orange hue, then maybe WB, but grey is likely due to it not being lit sufficiently in comparison to the main subject.
I think a major question is, was it white to begin with (i.e. in real life)? If so then your white-balance is off, but that can be easily adjusted in Camera Raw or Lightroom, not sure how to in PS.
If I'm way off here then ignore me lol.
You are way off here
Grey is just dark white, WB correction is used to correct / change colour casts.