If you see 10s countdown and game won't connect it means that there is a connection problem.
Thing you could try:
Start a coop session (go to skirmish or campaign and click invite friend to invite some steam friend to play with you)
Coop is hosted P2P meaining data won't go to our server and so it should work.
If coop does not work either, It is likely that whatever blocks network is close to you (route, ISP) - make sure you have UDP protocol allowed.
If coop does work, it means that access to our server is blocked for some reason.