Are there any more details you can give us? Such as the exact wording of any error message? Or EXACTLY and in great detail, what happens when you try to start Lightroom?
I had a previous version of LR but I bought a new camera that was not supported by it. I updated to version 6 from B&H Photo the install seemed ok but after the initial screen launched and I clicked on an image the screen froze and i says not responding