Ask HN: Why can't I submit a new self post?

Only the moderators would know exactly why. Try the last entry on https://news.ycombinator.com/newsfaq.html or email hn@ycombinator.com

I have to guess ... because you submitted the same question from another account two weeks ago https://news.ycombinator.com/item?id=17949299

For an oficial answer from the mods, send them an email.

Sometimes there are blocks new accounts to reduce the risk of spam.

But as gus_massa pointed out, this question was asked a few weeks ago (by another account of yours?).

And, for what it's worth, it's not a great discussion topic for HN anyway, as it's a question that is fairly easily answered with a couple of Google searches.

Good Ask HN topics are those that prompt people to share their unique personal experiences.