Why does Search Console say my sitemap couldn't fetch when it opens normally in a browser?

A sitemap opening in your browser only proves it works for your browser right then; it doesn’t prove Googlebot could fetch it. In Search Console, open the sitemap details, then run a Live Test on the exact submitted sitemap URL in URL Inspection. You want crawl allowed and a successful page fetch. Check for a robots.txt rule blocking the sitemap, a typo or old HTTP/www URL in the submission, server/CDN behavior that treats Googlebot differently, and temporary availability problems. Search Console also notes that fetch failures can be transient, so if the live test is clean and the server is stable, wait for another Google fetch before changing everything. Fix any confirmed issue, then resubmit the sitemap.