Update: Blizzard says the problem should be fixed. "Servers should be available again in all regions," Blizzard Customer Support tweeted. "We will continue to monitor performance. We've also applied a fix that should help unlock characters and will continue to review for any we've missed."
[#D2R] Servers should be available again in all regions. We will continue to monitor performance. We've also applied a fix that should help unlock characters and will continue to review for any we've missed.September 23, 2021
Diablo 2: Resurrected launched today, and it's having a bit of a rough start. Multiple players are reporting on Reddit and the Blizzard forums that their characters and progress are disappearing after play sessions, forcing them to start over again. One lost their character after beating all of Tristram, Diablo 2's first area—a frustratingly big chunk of the game to power through so quickly and then lose.
The good news is that it's probably (or at least hopefully) not an unrecoverable error, but just some server jankiness. This sort of thing happens from time to time: Similar issues have cropped up previously in World of Warcraft, for instance, such as when players on the Khadgar server were "de-leveled" in 2020. It's common enough that Blizzard has a support article explaining what players should do before bugging them if their characters go missing.
Whatever the problem is, Blizzard is aware and working on it.
Offline play should remain available for all players who have already authenticated.September 23, 2021
Unfortunately, the estimated 30 minutes to get things cleared up doesn't seem to have held, as Blizzard said about an hour later that it is "continuing to work on problems affecting characters and game creation."
We'll keep an eye on the situation and update when Blizzard sounds the all-clear. In the meantime, if you're just trying Diablo 2 for the first time with this new edition (or are waiting to), we've got a character build guide that can get you started on the right foot—and if you're looking for a more contrarian take on the whole thing, here's Fraser on why he thinks Diablo 3 is actually better than Diablo 2.