I get the error message “Failed to Join Game” for any offline character and online characters fail with the message “An issue occurred while communicating with the game servers. Please check that you are connected to the internet and try again” – yes. I am connected to the internet.
How can I fix
You cant, Blizzard has done this intentionally.
wdym, i paid to play this game tf is going on?
Online and offline chars cannot mingle.
Offline chars could be easily manipulated. And in theory, on-line not. So if you wanna play online you need to create an online char. And then decide whether it is a ladder char or non-ladder. (And of course SC or HC, but that exists offline as well)