If you are a returning user getting an error message when trying to create a profile for online multiplayer gaming and are getting error message like error 3.13 “unable to connect to battle.net, try again later” See below:
There is a very simple workaround for most people who have this issue.
Follow these steps:
Instead of setting up your account using an email address that has already been used for blizzard gaming, create a new battle.net account using a new email address or one that has not been used for battle.net / blizzard games via the create new account in the blizzard app.
Once you have that set up the game will let you create a new profile so you can play online.
After that you can logout of the new account and log into your old accounts that have your friends list, settings, stats and so on.