When you ask a question you need to provide some basic information
Mac or Windows, and EXACTLY which version of the operating system?
Recent Mac AND Windows operating systems have been known to cause "odd" problems
Are you using a computer Administrator account with full read/write permission?
As highlighted by John, you need to provide more information.
Which operating system : Mac or Windows?
Does it read any message at the screen where it hangs?
Also, make sure that the program is updated to Lightroom 6.4 : Keeping Lightroom Up-to-Date