Just installed the game though the Battle.net application and after launching it and getting to the main menu, when I click on “Create New” button under local section I get an “Unable to Connect. You must launch Diablo II: Ressurected through the Blizzard Battle.net launcher”
How do I solve this?
Having the same issue here, can’t make a character, launched the game through the Battle.net launcher as stated, tells me I haven’t. Disabled all my firewalls, restarted the game/launcher/computer multiple times, even reinstalled launcher, did not work :< Would love a fix as I was happy to get access but can’t even play! (In EU if that affects anything).
EDIT: Managed to fix it, you need to launch the game under ‘Americas’ in the ‘Regions’ section where it says ‘Game Version’ in the launcher (just above the big ‘Play’ button). Hope that helps!
Thank you for this! It’s working now!
Thanks for updating this post with your resolution!
Having the same issue
Changing region to ‘America’ doesn’t help 
Same issue. But I also think maybe they closed the Alpha at 1pm EST today
Q: How long will the Technical Alpha last?
A: The Technical Alpha will run until 10:00 AM (PT) on Monday, April 12th.
Understood, but … How is it possible that twitch is full of people who can still play? Can you explain that please?
Perhaps they were logged on when things went down and they can now stay connected until they log off?
The trick was not to leave your character/game.
So I finally got this alpha running on a Windows 10 machine and now I am running into the OP’s problem.
If I had to guess, the message we are seeing is a generic placeholder for being unable to connect to the Diablo 2 World or Authentication Server.
Edit: Nevermind. If the Alpha is over then tyhat would be why I can’t create a character…