From GameWatcher: “Rainbow Six Siege is one of the most popular PvP FPS titles on the market for a reason, but even with all the polish it’s been getting, problems do pop up from time to time. If you’ve been dealing with Rainbow Six Siege matchmaking problems, chances are that you’ve come across Error 2-0x0000d00a”
Source: N4G PC Rainbow Six Siege Error Code 2-0x0000d00a – What Does it Mean?