Original sentence: If manually configured the problem can be improved, but not fixed.It was found that the problem originated from the ESO server and not the game itself, namely bad port configurations.The complete list of port numbers used by the server was not updated in each individual game.There are reports of people unable to join games on ESO with the "Failed to join" error
Edited sentence: An investigation by an independent network engineer using a network analyzer has concluded that the problem originates from ESO server and not the game itself, namely bad port configurations.Even then the player may be disconnected if another player in the same game has the wrong configuration.In addition, there are several reports of people not able to join games on ESO with the "Failed to join" error.In short, the ESO forgot to give the client players all the port numbers used by the server.One would need to manually configure the router and firewall to authorize the needed ports