What would cause hair dye not take in hair all of the sudden and not talking about box dye talking about go to the salon and dyeing hair?

This can happen if your hair is a dark colour, Say your hair is black and you go to the Salon to go blonde, If the person doing your hair does not use enough of the chemical called Peroxide your hair wont go that lovley blonde you want it will turn a coppery ginger, Where as if your hair is a dark brown and you want to go a few shades lighter the colour has less chance to take, I suggest going to Sally's and getting a couple packets of Bleach powder and 2 bottles of Peroxide and bleach your hair for 30 minutes-1 hour and then go to the salon to go to a brown or blonde colour, But you should be very careful with how manytimes you bleach your hair in 3 months, This much chemicals can cause hair loss.