Indexable pages are missing from the sitemap
What this means
The crawl found indexable pages that no sitemap declares. Google will usually reach them through internal links anyway, but on a large or shallowly-linked site the sitemap is how deep pages get discovered promptly.
How to fix it
Include every indexable page in the sitemap. If the omission is deliberate, confirm those pages are genuinely well linked from elsewhere on the site.
Fix effort
This check needs a developer fix: it turns on a routing, hosting or infrastructure decision that no automatic edit can make safely.
Authoritative source
https://developers.google.com/search/docs/crawling-indexing/sitemaps/overview
Find every page this affects
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