This is a known issue and Our Engineering team is working on it.
Please follow this link https://helpx.adobe.com/lightroom/kb/thumbnails-display-black-in-lightroom-6-2.html
Here is a Duplicate thread:-Lightroom images turning black
Let us know if that helps
Thank you Akash for the acknowledgement. Chetna provided a workaround and it has proved to be viable for the time being.
Thanks Akash and Chetna. Any chance I can extend my evaluation? It is most likely that I will continue my solution with Lightroom CC.
The Evaluation Period is only for 30 days to try and grasp how the Product works.
Buy the Photography plan as you have the option to Pay a easy Monthly Payment for your Subscription
There are many other exciting Mobile Apps Bundled in the Plan to make it a One stop Solution for Photo Editing on Desktop /Phone/Tablet.