Which tool are you talking about?
Try resetting the preference of Editor and see if that solves your problem:
I believe you are talking about "make dull sky blue" in quick edit. It can only enhance the color in the section of the image having the sky. It can not convert gray sky to blue. You can look for a few methods to replace your gray sky to a blue one.
Here is a way to create your own blue sky using a gradient.
Europe, Middle East and Africa