How can I find out why my question wasn't posted?

There is a prefilter the question has to pass. If you have links or references to certain websites or certain keywords, the questions will be held for staff review, usually 30 minutes to a couple of days. If there is a problem, you may get a violation or they may just not post the question. If the question is showing in your profile, this would be the reason. Ground zero questions are probably being highly reviewed.

If not in your profile, they could have been quickly deleted. There is a rare random glitch, but that hasn't been reported in months.

Try this. Edit the question and add just a couple of periods in the added details and resubmit. This sometimes clears the question. Or post with no links and add them in the added details.

In essence, you can't find out.

Even the Y!A Staff cannot tell us that.

I've surfed the Y!A Suggestion Board, and the reason questions don't post is gilded over and / or left unanswered by staff.