how to replicate this bug:
first, fully join a server( meaning you need to fully load it, you able to move, interact with the server)
then tab out, such as reading emails or focus on other applications( for Windows 10, switching desktop )
then the game will "kick" you out from the server,
after that, when you tried to rejoin it will show either of the message shown in the pictures

to rejoin servers you will have to restart the game,
however, if you pressed disconnect, then tab out, this bug won't be here.