Hi!
I was having a problem similar to this. In my case, the problem was that Microsoft OneDrive was making my folders under Documents a “cloud type”.
You can check it under “C:\Users\your user\OneDrive\Documents”. Usually its going to show a column named “status”.
If it shows you a little cloud icon as the status of the Warcraft folder, than you can right-click on the Wacraft folder and select the option that says “Always keep on this device”. This way all of your files are going to be downloaded (it may take a while), and will prevent OneDrive from uploading your files to the cloud and ereasing them from your PC in the future. Only launch the game after you download everything (the icon is going to change to a green check symbol).
If this is your situation, W3 gives you a black screen and freezes because its waiting for all of the files to be downloaded from OneDrive. Every time you close the game, OneDrive uploads all the files and than deletes from the local storage. And everytime you launch the game, everything needs to be downloaded again.
Hope this helps.
(sorry for my english, its not my native language)