It appears that something is afoot for the online components of the first Dark Souls game to hit PC. According to a thread on the BandaiNamco boards and a reddit thread, the online components for Dark Souls: Prepare to Die Edition have not been working for the past six or seven days.
The cause is currently unknown, though it is believed to be a change in a configuration relating to the game's online components in a variable called "usemms" which was caught by SteamDB several days ago. It's been theorized that this variable stands for the use of a matchmaking service, but this is so far unconfirmed from official sources. However, many users have noted that the change in the variable reported on SteamDB to an empty placeholder took place at the approximate time that online features ceased to work.
For a quick elaboration on what this means, many configuration files use a binary switch of either a 0 for "off" and a 1 for "on" when manually configured in a text file. An empty character could also be used to disable a feature in a config file, depending on how the game in question is programmed. While the "usemms" variable in question is currently 1 to turn it on, it appears to not be functional.
Dark Souls uses it's online features for more then just traditional multiplayer in either co-operative or pvp modes which makes this impact also harm the single player experience. Without the online server functionality, the game will also not be able to show bloodstains and messages which are a part of what the series uses for players to pass on hints or the game to give a warning of danger ahead by showing that someone else had died recently in the region and what they were doing.
The timing for this is when many Dark Souls fans are playing the latest entry, Dark Souls 3, which like Dark Souls 2 is not impacted by this. Bandai Namco has said that Dark Souls 3 is their fastest launch title in America ever, although they refuse to provide any numbers on that.
So far, the only official responses from the official Bandai Namco twitter handle mention that the team is looking into it. TechRaptor has reached out to Bandai Namco for comment and we will update as soon as we have any more information on this problem.