Something about blizzard’s auth service broke, it’s being reported in WoW forums too.
In the meanwhile, you can launch Overwatch by going to
[OVERWATCH_FOLDER]_retail_\Overwatch.exe
And launching that, you’ll skip battle.net altogether.
“Program Files (x86)\Overwatch” Is the default install location, if you haven’t changed it and aren’t sure where to look.
ur welcome 