I've got same problem as you had. I'm unable to connect on my account for a hour right now.
Not trying to hijack this thread, but i get this from time to time. Especially when i am using Poolfisher bot and i have to force close it since it has a bug. Whenever i restart WOW and HB, i get max sessions, i just keep clicking on it and exiting it until it attaches. Sometimes it takes about 5-6mins, but i get it back on. And yes, i always go to the page and it will show no current session online.
trying to catch you, you are offline....
started working again......
except for the intermitten max sessions when closing between character changes