Google webmaster sitemap xml namespace error
Change the opening <urlset> tag to look like the following
<urlset xmlns="https://www.sitemaps.org/schemas/sitemap/0.9" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://www.google.com/schemas/sitemap/0.9 https://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd" xmlns:image="https://www.google.com/schemas/sitemap-image/1.1">