Since the sitemap.xml file is not accessible directly, you can use this page to generate a sitemap for Google Search Console.
Google Search Console allows you to submit individual URLs. Here are your most important URLs to submit:
You can submit these URLs one by one in the "URL Inspection" tool in Google Search Console, then click "Request Indexing".
You can create a sitemap.xml file on your computer and upload it directly to Google Search Console:
You can use a third-party tool to crawl your website and generate a sitemap:
If you're still having trouble with the sitemap, consider reaching out to Vercel support or consulting with an SEO specialist who can help diagnose server configuration issues.