Command and conquer 3 tiberium wars login failed - can't connect to server

I was having this same problem.  I would attempt to activate the game, but it would complain that it could not access the server.  I was finally able to track down the problem to having my Origin games installed on a different drive than the Origin executable.  In order to fix this problem, I created a soft link between the default install directory, "C:\Program Files (x86)\Origin Games" and my actual game install directory. This is the command I used:

mklink /J "C:\Program Files (x86)\Origin Games"  "[Actual Install Directory]"

I hope this helps,.