I have the same problem since about a week now. Sometimes the game works fine, plays for about an hour or two then disconnects and unable to connect to the server again.
I've changed no settings from the time it was working fine, a VPN seems to allow connection, checking the game and re-downloading the game, but as soon as you load into the game it immediately disconnects again. Turning the VPN on and off grants connection somehow but only briefly and disconnects as soon as you log in.
Is this a measure to prevent DDOS attacks or something? @Observer could you help maybe? Thanks a lot in advance