For the grey issue, please try unchecking graphic processor in the preferences.
Click Lightroom -> Preferences -> Performance
Uncheck Use Graphic Processor
Close Lightroom and re-open it.
And auto tone issue is something that we already know about that and that soon will be fixed.
Please check this article : https://helpx.adobe.com/lightroom/kb/thumbnails-display-black-in-lightroom-6-2.html
Turns out the Intel HD 4000 graphics card In my Macbook Pro which is less than 2 years old, is 'unsupported'!!! Thanks Adobe!
How do I role back to a previous version?
It's not Adobe's fault that your card hasn't got the spec to deliver GPU acceleration, Steve - 2 or so years is a lifetime in computer hardware/software development terms.
Can't except that Keith, I have no idea what GPU acceleration is, and what you are saying is that I have to spend £1000 every year on a new computer. I now can't have any more Lightroom upgrades yet I still have to pay for it every month. So I am paying for upgrades that I can't have unless I buy another computer.