Sitemap exceeds 50,000 URLs
What this means
A single sitemap file may hold at most 50,000 URLs. Past that limit the file is rejected, and every URL in it goes undiscovered through this route.
How to fix it
Split the URLs across several sitemap files and reference them all from a sitemap index.
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/large-sitemaps
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