@nhattruongvu
I understand Google is showing that it is unable to read your sitemap. To address this, we suggest the following actions:
1. Clear all your caching from your theme, plugin, server, CDN like CloudFlare or browser. If you are not sure how to clear caching from theme/plugin please speak to those authors. If you want to clear cache from the server, please speak to your host provider. To clear the cache from a browser use this guide: https://yoast.com/help/submit-sitemap-search-engines/
2. Delete your sitemap in Google. Doing so will not hurt the SEO of the site. This guide explains more (scroll to the bottom): https://support.google.com/webmasters/answer/183669?hl=en.
3. Submit the sitemap again. Be sure to submit only sitemap_index.xml and nothing else. This guide explains more:
4. Monitor the results to see if the issue is resolved. It can take some time before Google can report on the crawled URLs after you re-submit your sitemap. Google Search Console reports?are not real-time.
Please let us know if you have any questions; we’re happy to help.