Some more info may help-
Do you see your image previews in the Library Grid view?
Can you select one image and view it in the Develop module.?
Can you make global adjustments to an image in the Develop module? (eg. Exposure)
So you cannot click on an adjustment tool to make it active?
Yes, I can see the image previews in t he Library Grid view.
I can select any image, and view it in the develop module. However, all the tools in that module are inactive, and I can't use the button in the tool stop activate them.
I can adjust the tone curve directly in the chart, but i can't use the handlers, since they're not activated.
There's no thumbnail in the navigation tool.
all the tools in that module are inactive,
So in the Develop module, you cannot click on the Adjustment Brush tool to make it active?
If you press [K] does the Adjustment Brush become active? [Q] for Spot brush. [M] for Gradient tool.
Can you use the sliders in the Basic Panel to make global changes to your image?
Is it possible that Adobe thinks your LR is past a 30-day trial, and has deactivated the Develop module?
It seems you are trying the correct things (Re-installs & reset preferences) so it might be time to talk to adobe direct.