I have C & C Red Alert 2 and Yuri's Revenge (Origin) and thereafter CNCnet installed. But after starting the CNCnet client lobby remains empty - without any error messages. 
  
I have started several times, it never happened, as can be seen in the screenshot. 
  
Also I have disabled the firewall, unfortunately, it does not change. The log file I've attached - if more information is needed, just ask. 
  
System: 
Windows 7 64bit 
Microsoft .NET Framework 4.5.2 is installed 
  
 
cncnetclient.log