I've seen numerous related threads floating around all with the same basic issue. I simply can not join a multiplayer game. Either while connecting to the server or a few seconds after making the connection, I will be disconnected and receive the error message "Connection to Server is Lost." I've tried finding the answer myself having tried the proposed solution in this thread
with no success. I also found people claiming the issue was in the file "rgl_log.txt". "use_secure_connection" needed to be set to 1 or 0 to fix the error. The odd thing is that I tried that and it actually worked! For a few days at least. Since then it has reset to a 0. I've tried to change it but it keeps reseting itself each time I run the game.
I've uninstalled and reinstalled the game through Steam hoping that would work, simply gave it time, etc. so I'm finally here asking for personalized help. Perhaps what might be more unique about my case is that Mount and Blade never prompted me for my validation key so I can't help but wonder if that's the issue. Steam specifically told me my key and every time I launch the game it tells me that it will ask for it and to answer with the following key. Despite all this talk about validation I have never been asked and as mentioned earlier I was actually able to play for a few days without ever verifying.
It's all speculative of course because I have absolutely no idea what's going on. I'm just trying to help someone find the solution for me by giving all the information I can think of. I appreciate any help.