.xml sitemap "unsupported file format" next.js

I'm getting ready to launch my first client project using next.js and I've fallen at the last hurdle. I have an obscenely simple .xml sitemap in my next.js project and google is not accepting it error from google search console is "unsupported file format"

<xml version="1.0" encoding="UTF-8">
  <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
    <url>
      <loc>http://jeannette-skibbe.berlin/</loc>
      <lastmod>2022-05-05</lastmod>
    </url>

    <url>
      <loc>http://jeannette-skibbe.berlin/contact</loc>
      <lastmod>2022-05-05</lastmod>
    </url>

    <url>
      <loc>http://jeannette-skibbe.berlin/about</loc>
      <lastmod>2022-05-05</lastmod>
    </url>

    <url>
      <loc>http://jeannette-skibbe.berlin/portfolio</loc>
      <lastmod>2022-05-05</lastmod>
    </url>
  </urlset>
</xml>

I copied the sitemap structure from the next.js docs and the sitemap is reachable under https://jeannette-skibbe.berlin/sitemap with the sitemap being in the "/local" file.

Please help a girl out x

Update:

Solved issue at last. amended code below.

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>http://jeannette-skibbe.berlin/</loc>
    <lastmod>2022-05-05</lastmod>
  </url>

  <url>
    <loc>http://jeannette-skibbe.berlin/contact</loc>
    <lastmod>2022-05-05</lastmod>
  </url>

  <url>
    <loc>http://jeannette-skibbe.berlin/about</loc>
    <lastmod>2022-05-05</lastmod>
  </url>

  <url>
    <loc>http://jeannette-skibbe.berlin/portfolio</loc>
    <lastmod>2022-05-05</lastmod>
  </url>
</urlset>

Essentially I was unfamilair formatting the xml seems that the ? merks in opening line act as a self closing element.