Diablo 4 is finally out in Early Access and Blizzard is investigating login issues and error codes

gamesradar.com:

After many long years, several successful betas, and so, so many launch trailers, Diablo 4 is out in the wild - at least in Early Access - and as you might've expected, players are reporting queues and error codes preventing access to Sanctuary. Fortunately, Blizzard has already acknowledged the issues.

We know this song and dance well by now here at GamesRadar+, having reported on the countless live-service launches whose servers struggle and often buckle under the crushing demands of hundreds of thousands of players trying to log in all at once. And yet, despite Diablo franchise boss Rod Fergusson ensuring us Blizzard was "prepared" for Diablo 4's launch, it's frankly unsurprising that players are running into long queues, error codes, and the like.

Over on Reddit, in an ironically titled thread foretelling "the smoothest launch ever," there are dozens of complaints from players eager to get into the game during its Early Access launch. One particularly prevalent error code seems to be reported mainly by PlayStation users, and it's telling people they have "no valid license." Blizzard has acknowledged this issue and says "more information" is on the way. You can follow the official forum post from Diablo 4 community manager Adam Fletcher here.

We are looking into the Invalid License issue that some PlayStation users are reporting. We will update this forum thread once we have more information.https://t.co/U1KKQtQ4OWJune 1, 2023

I haven't experienced any error codes trying to get into Diablo 4, but my RTX 3060-equipped laptop crashed as the opening cinematic was just starting to play. My Battle.net launcher currently has a message that reads, "We are investigating reports of login issues affecting Diablo 4 and working