A few of the most recent posts are already mentioning this issue. I am also suffering from it.
I think it was two days ago that I did my usual post-season cleanup, sorting out my inventory and stash a bit, then deleting my formerly seasonal character. Then last night I tried to log on since I read the event is currently ongoing to get Kanai’s Scorn which I don’t think I have yet, but this is when the error began. After some googling I’ve tried the Bnet repair tool (no problems detected), tried waiting 10+ minutes, tried deleting my battle.net folder, tried switching regions, and basically nothing has worked and I can’t play on my normal region anymore. Decided to let it sit and I’ll just wait, and tried again today. Success! I was able to log on as the first character in my hero list. That hero was not properly built though so I left game to switch characters, and upon attempting to do so, I am now back in error 395002 land for all characters including the one that had just worked for a brief moment.