There is a BN 564 Overwatch error that is plaguing users across all platforms, though, it does seem to be mostly for players on PS4. The BN-564 error causes players to be unable to login to the game online, which prevents them from of course playing any online matches. This is an unfortunate error.
The BN 564 Overwatch error can be caused by quite a few different things, but thankfully, it does have a direct fix unlike most errors for the game. However, it can also be caused by issues on Blizzard's end, especially if there is maintenance currently or if there's an impending update.
Overwatch BN-564 Error Explained: How to Fix BN 564 Overwatch Error
The BN 564 Overwatch error is caused by the player being unable to login to the game online. This issue can be because of one of two problems. The first problem is, like we mentioned above, if there's maintenance currently going on or if there is an update about to be dropped.
If that is the case, the maintenance ending or waiting and downloading the new update will fix the problem for you. You can check the status of the game and if one of those is going on right now by heading to the game's official Twitter. If none are occurring, then there is a different reason for why you have the BN 564 Overwatch error.
The other reason why you would receive the BN 564 Overwatch error is an odd bug that occurs every so often for random players. It mostly affects PS4 players but some Xbox One players deal with it, too, and it has to do with your PSN (or Xbox Live) account that is linked to your Battle.net account.
To fix this BN 564 Overwatch error, you must go to Battle.net, login to your game account, navigate to the security tab for your account, then accounts, and select to unlink your PSN or Xbox account. This will fix this odd bug and let you log back in.
Update (March 8th, 2018: 10:49am PST): We have received word that there is another issue that is causing servers to be down. Check out this for more information on it and what you can do.