Ryzen 7 3700, I can’t load classic era and have never been able to load hardcore.
I actually had this problem with my retail client as well when the WW prepurchase went live. The fix for that was super simple, deleting cache folder. Nothing I’ve tried has worked for classic era or hardcore.
Edit: right after I posted this, I had classic era idling on a black screen. Tab’d back in after 10 minutes to a cinemtaic.
It appears to be an authentication issue. I finally got to the login screen of classic era and it’s asking me for an authenticator, even though I migrated all that ages ago. And it’s not sending my mobile a notification either.