Blizzard have posted a known issues list for the beta, as well as tweeted about an authentication issue affecting servers. 

[#Diablo4] We’re currently investigating an issue affecting our authentication servers, which may result in failed or slow login attempts.

— Blizzard CS – The Americas (@BlizzardCS) March 17, 2023

Known Issues (Source)

PC

The Diablo IV Open Beta is available for Early Access beginning March 17th at 9am PDT and ends on March 20th 12pm PDT. Open Beta will be available beginning March 24th at 9am PDT and end on March 27th at 12pm PDT. The below are known issues with the build that players should be aware of.

We will continue to update this thread if any other known issues arise throughout the beta weekends.

Known Issues

If the player triggers the Lorath introduction cutscene while the world is in daylight, the player’s and Lorath’s shadows will shimmer in-game until the Prologue is complete. This issue will not occur if the player skips the cutscene.

In-game voice chat may not function correctly for all players.

Performance optimizations are still in progress. Players may encounter some performance issues, particularly on older hardware across different platforms.

The ‘Play’ tab at the top of Character Selection is clickable but currently does not lead to another menu in the beta.

Users may experience a queue while logging into Diablo IV during Early Access Beta Weekend. Please note that the countdown may finish and go beyond the duration listed on the queue timer. Do NOT leave the queue as this will restart the queue. We will have more accurate timers in place for Open Beta Weekend.

During the beta players will be able to select from a wide variety of work-in-progress “Text Language” options beyond English. English will be the only available option for “Spoken Language” during the beta, but other languages will be available at launch.


Console

Known Issues

If the player triggers the Lorath introduction cutscene while the world is in daylight, the player’s and Lorath’s shadows will shimmer in-game until the Prologue is complete. This issue will not occur if the player skips the cutscene.

In-game voice chat may not function correctly for all players.

Performance optimizations are still in progress. Players may encounter some performance issues, particularly on older hardware across different platforms.

The ‘Play’ tab at the top of Character Selection is clickable but currently does not lead to another menu in the beta.

Users may experience a queue while logging into Diablo IV during Early Access Beta Weekend. Please note that the countdown may finish and go beyond the duration listed on the queue timer. Do NOT leave the queue as this will restart the queue. We will have more accurate timers in place for Open Beta Weekend.

During the beta players will be able to select from a wide variety of work-in-progress “Text Language” options beyond English. English will be the only available option for “Spoken Language” during the beta, but other languages will be available at launch.

Player 2 may experience issues joining games with a pre-existing hero while playing couch co-op during the Prologue.

Players playing Hardcore in local couch co-op on console may not be able to return to character select until both players die. This will be addressed at launch.