I've submitted a sitemap to my website and Google Search Console status is "Couldn't fetch". I've had my xml verified by XML Validation, and my xml is also publicly available to be viewed.
Google's support website suggested troubleshooting "Couldn't find status" with the URL inspection tool. I wasn't able to find anything useful from that asides that my sitemap hasn't been crawled. See the screenshot below:
XML:
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://sitemaps.org/schemas/sitemap/0.9">
<url>
<loc>https://simplyharmonica.com/</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>1.0</priority>
</url>
<url>
<loc>https://simplyharmonica.com/harmonica-for-beginner</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/different-types</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/blues-diatonic-harmonica</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/blues-diatonic-harmonica</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/chromatic</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/holder</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/hohner</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/lee-oskar</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
<url>
<loc>https://simplyharmonica.com/marine-band</loc>
<lastmod>2019-03-27</lastmod>
<changefreq>yearly</changefreq>
<priority>0.8</priority>
</url>
</urlset>
EDIT: Solution found here and also adding www.
before sitemaps.org