I never needed to talk to the battlewarden. But they are gated by level. But, the Basic Training one is the first at level 10, so clearing it should unlock the next as long as you're level 10+ (which obviously you should be if you've got the first).

Are you running them unsynced, maybe? Dunno if that could prevent it from being counted as complete. If it's registering as complete, the image icon in the Duty Finder window for that 'hest should have a green check mark on it. If you've got the check mark and have run it synced with a party, I'd probably call bug.