What is the frequency of sitemap reading by google/yandex bots?

Question

Search engines

Interested in the sitemap, not the Sitemap index.
I ask because bots seem to run around the sitemap index, but they can’t reach the sitemap in any way.
The first time I ran it, but with an error (now I seem to have corrected the encoding), and that’s it, it hasn’t read for 9 days, although the lastmod for it in the Sitemap index is indicated every day fresh.

Answer 1

Focus not on the Sitemap, because. it is only an indication to Google about which pages you, as a webmaster, consider important.
See crawl analytics: Google Console - Legacy Reports and Tools - Crawl Statistics:

This is more informative, though admittedly not enough information.
Encourage Google to crawl your site more often and deeper.