Had same issue, Windows 10 1903 update was waiting so restarted and let it install and game launched as soon as I clicked play. No waiting for game to prepare window or anything.
So check to make sure there are no Windows updates waiting. Hope this helps.
I have not been able to play for nearly a week now due to this issue. Update? Fix? Anything? Your really letting me down here blizz…
I found a fix. I let it stay stuck, watched a movie, took a 4 hour nap, came back and it finally did something and was done. Heh…
Thanks! This worked for me 