Method 1: look at the best post in reddit that describe your niche/subject URL and post that URL their.
Method 2: open an account in google publisher center when approved it makes your indexing faster.
Google has been experiencing crawling and indexing issues for some time. It might also have decided to not index your content because it's too thin or of too low quality.
I've experienced the same issue recently. A URL with a trailing slash is indexed, while the one without a trailing slash is not. Google says these are duplicate pages. Weird.