I can only confirm, at first time when I enter for example if using Yoast SEO plugin for WordPress, the URL to the sitemap into the Google Search Console, it always gives me an error or like error while fetching your sitemap while it actually can be accessed - but maybe it wasn’t generated before, so server would have few seconds longer to generate all of them, meaning the GSC would I do not which error or timeout get and show it as “unaccessible” in the dashboard.
It get’s normally after an hour or next day I see it indexed already.
I can access the sitemap via URL https://fry-electronics.com/sitemap_index.xml.
Therefore, when validation your XML sitemap, looks fine, but I think you are missing out the below on the starting <sitemapindex> tag as it should be: