The dehaze slider is under the "Effects" tab in the develop module. Did you check there?
I also couldn't find it right away
What version of Lightroom do you have installed?. Go to the Help menu and look next to "About Adobe Photoshop Lightroom..."
The updates do not happen automatically, have you updated your Lightroom software recently?
I have noticed that my copy of Lightroom CC sometimes gets a little confused about being CC or 6.x. Logging out and back in (or restarting) seems to solve the problem and bring everything back to CC status.