What's going on with Diablo II battle.net?

I am a loyal player of diablo2 for years. I recently purchased again diablo2 on blizzard official website and downloaded the game from the website, but I cannot successfully log in to battle.net. I don’t know where the problem is. Anybody can help solve it? If this game can no longer run, why are you still selling it? I really like it.

Thanks!