Help! Can't log in!

Hey everyone, I hope I am posting in the right spot. Anyway I went afk to get a drink of water and grab some snacks, and when I came back it auto logged me out, which is normal. But every time I try to log back in, it shows a black screen and the chat box empty and nothing else. I don't know if the server is down or if I need to reinstall java, but does anybody know why this is happening or what I should do?
Thanks!
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Guess I'm just unlucky xs