[Update 12/17] Treyarch has released a new CoD: Black Ops Cold War and Warzone Update that should fix the 'Zed 398 Swift Clover’ error that prevented players from playing Season One content.

　　We've released a new update this morning to fix the “Zed 398 Swift Clover” error on PC and an occasional hitching issue on PS5.

　　We'll continue to monitor; in the meantime, grab the download if you haven't already and jump into Season One!

　　— Treyarch Studios (@Treyarch) December 16, 2020

　　[Original story] Call of Duty: Black Ops Cold War and Warzone PC crossplay has been temporarily disabled as developer Treyarch is looking into the ‘Zed 398 Swift Clover’ error that players are experiencing.

　　Yesterday, the new Cold War update went live followed by a separate patch for Warzone this morning. This update merged Warzone with the latest Call of Duty installment and introduced the new Season One content, but apparently, the new update is causing an unforeseen problem for players attempting to play the Season One content.

　　Various players, especially on PC, have been reporting the so-called ‘“Zed 398 Swift Clover” error which prevents them from joining the new content in multiplayer games. At the moment of writing, a fix for this error hasn’t been released just yet, but Treyarch has said that it’s actively investigating the issue with the developer of the PC version of the game, Beenox. In order to keep the game lobbies healthy and full, crossplay between the various platforms has been disabled on PC until the issue has been resolved.

　　We are aware of the current “Zed 398 Swift Clover” error when attempting to play Season One content on PC, and our partners at @BeenoxTeam are actively investigating.

　　To keep lobbies healthy and full, crossplay has been temporarily disabled on PC while a fix is investigated.

　　— Treyarch Studios (@Treyarch) December 16, 2020

　　Call of Duty: Black Ops Cold War and Warzone are available now for PC, PlayStation 5, Xbox Series X|S, PlayStation 4, and Xbox One.