So I am at my character selection page and I get this
You have been disconnected. (WOW51900325)
If I hit escape and reconnect it goes away but it’s been a problem for awhile , I noticed it started some time last expansion when I played through Season 2 and Season 3 but then took a break in S4 and camed back to the game in DF.
I am not sure, but I think it is related to separate services within the Bnet universe. It may think one is disconnected, such as Bnet chat, but you are not disconnected from the game.
I get it too sometimes, and have for over 10 years. It normally does not impact the ability to just switch chars and enter a game. I just ignore it.