Right around the time Dark Souls 3 launched, the multiplayer portion of Dark Souls 1 started having bigger and bigger issues until it inevitably succumbed to the hollowing process, and just stopped working.

Its been almost a week since it has gone down, and there is still no official comment from either Bandai Namco or FromSoftware. The only actual piece of information I could find about Dark Souls 1's technical troubles was a short tweet from a community manager, posted 5 days ago:

"RE: Dark Souls PTDE Matchmaking. Not sure why it's being funky. Have made dev team aware - Will share any updates."

Given the maddening silence from whoever is in charge, the community has started coming up with conspiracy theories, the most intriguing one being that the Dark Souls 1 servers were taken off and re-purposed to help with Dark Souls 3's overwhelmingly strong launch. While it certainly is possible for Bandai Namco to do this, I wouldn't be so hasty to point fingers as it could just as easily be a technical issue that is currently in the process of being solved. I will, however, offer no excuses for the lack of communication, because if a service goes down for a week, the customers deserve to know what's happening.

Until this whole mess gets resolved you will not be unable to invade other players, engage in jolly cooperation, see the bloodstains of poor fools that believed the "Jump Here!" sign, or even send messages between worlds. I will update you once more information is released, and hopefully a fix along with it.