[quote=@Birdboy]
[ h 1][center]Da Rules![/h1][/ c enter]
[/quote]

It's because you have the tags in the wrong order. You need to close them in the opposite order to how you opened them, so that the [center] tag is inside the [h1] tag.

[h1][center]Da Rules![/h1][/center] This doesn't work but...

[h1][center]Da Rules![/center][/h1] does.

Check the raw to see the tags I used.