It's very rare for an adult (over the age of 21) to be denied, and it's usually not a denial per se, but rather an error was received when the invitation was sent. When that happens, your application is marked as "pre-approved" and if you send LadyNightOwl a private message after you get your Central account situated, the invitation can be re-sent.
If there is a mistake in judging your age, please try not to take it personally. We can't see you nor can we ask for things like Driver's Licenses or Credit Cards in order to verify ages and our crystal ball is perpetually broken. The decision is almost entirely dependant upon how you respond to the application questions and how you conduct yourself while you interact with people on Central or in the game.