New post stuck at Discovered: Not Indexed

I published a new post for my blog 2 weeks ago – my 21st post. The first 20 posts were usually indexed in less than a day.

For about a week it was stuck in ""Page is not indexed: URL is unknown to Google". I eventually asked around and was advised to reupload my sitemap, which I did. The status then changed to "Discovered: Not Indexed" and it's been stuck there for a week.

"Test Live URL" brings up nothing wrong. I'm writing on a similar topic to topics that I've covered in the past. And usually the topical authority suggestion is given for pages that are "Crawled: Not Indexed", which is a somewhat different situation from mine.

I don't think my server is responding too slowly – my mobile page speed is 76 and desktop is 95 (which I know isn't the best, but my competitors have WAY worse speeds in general). Content quality shouldn't be an issue, it's a comprehensive guide written based on personal experience with several original photos.

Is there anything I can do to figure out a concrete cause for this?