Google has issues crawling your sitemap fileLet’s start with the most difficult scenario: Google can’t fetch your sitemap file. Sitemap index file errorsSometimes, Google may fetch your submitted file and detect errors. If Google fails to process URLs listed on the sitemap index file, you may receive an Invalid URL in sitemap index file error. Besides, your sitemap index file shouldn’t list other sitemap index files, only sitemaps. Once you have fixed all sitemap errors mentioned in your GSC report, resubmit your updated sitemap, and notify Google by pinging the updated sitemap URL.