Not sure if it will help but try to go to C(SystemDrive):\Users\YourUserName\Documents\Mount&Blade Warband (or just run a search for the following file).
Open the rgl_config.txt with any text editor.
Search for use_secure_connection =
Set that to 0 if it is 1.
Save and try if it helped.
If it is already 0 i do not know what else could be the problem
