Dark Souls tweets: “PvP servers for Dark Souls 3, Dark Souls 2, and Dark Souls: Remastered have been temporarily deactivated to allow the team to investigate recent reports of an issue with online services.

Servers for Dark Souls: PtDE will join them shortly.

We apologize for this inconvenience.”

Source: N4G PC PvP Servers For Dark Souls 3, Dark Souls 2, and Dark Souls: Remastered Temporarily Deactivated on PC