Google does not index all URLs on a website, that’s what Google’s John Mueller said on Twitter this week. Last month, John Mueller said that Google doesn’t index all pages in sitemaps or on the web, and that it would be impossible to do so.
It looks like a pretty long URL… we +/- never index all pages within a website, so that can be working as intended, even if you'd like to have more :). (Also, impossible to say without the URL)— ? John ? (@JohnMu) December 10, 2019
How to show Google the important pages of your website
Google has limited crawl resources. The deeper a page is buried on your website, the less likely Google will crawl it. In addition, the home page of a website is usually the website that has the most links from other websites, i.e. it has the highest PageRank in Google’s algorithm.
Check the click-depth of your web pages to ensure that Google indexes the right pages of your website: