Source
"One of the most frustrating Call of Duty: Black Ops 3 problems is the A.B.C. error message that some users see when they try to connect to a game.
If you see the A.B.C.-.-.F.G.-.-.-.K.-.-.N.-.-.Q.-.S.-.-.-.-.X.-.-. ?? error message on Call of Duty: Black Ops 3 there is a simple fix.
Restart the game. Wait in the main Call of Duty: Black Ops 3 title screen. That means do not press X or A right away. After about a minute an update should load. On the screen you will see a version starting with 33.1 instead of 33.0.
Once your PS4 has version 33.1.9.1 or higher and the Xbox One has 33.1.9.2 or higher you can proceed and you should no longer get the Call of Duty: Black Ops 3 A.B.C. error."