Unless you're a network technician, you likely have no idea what you're looking at when you're given an ironically short - or ridiculously long - error code when trying to log in or getting kicked out of your favourite game. So if you're playing Overwatch and running into error code BC-105, don't worry, you're not going to die.
Cropping up practically every week, error code BC-105 isn't anything to fret about. Maybe you don't look at the Battle.net launcher, Blizzard's news site or Twitter page all that often, but they're pretty good at pulling off hours of routine maintenance on a set day each week for each of their games. For most, this usually takes place in the early hours of Wednesday morning, but, depending on timezones, it can differ.
So for all those googling the issue this morning, let it be known the problem isn't with your system, game, account or Blizzard. The servers are likely still down or slowly coming back up. Sometimes you'll see others playing without any issues, but servers can't just take in thousands of players all in one go. It doesn't want to get overwhelmed.
Thousands of others await the exact moment Blizzard's games come back up each Wednesday morning, so congestion is still high a little while after. If you're seeing this message on a Wednesday, you're likely trying to access a server that simply isn't looking to play right now. Give it some time, check out the maintenance schedule and find something else to do. Maybe read up on some new tactics for your character of choice, perhaps.
Though you may start to see this at times other than routine maintenance - like during yesterday's authentication issues - rest assuring it isn't a problem you can just fix. It's something we all have to live with and learn to wait out.