my free XML sitemap generator keeps showing 'file not found' errors, affecting website indexing

hey everyone, so i'm pretty new to this whole SaaS thing and just launched my little web tool, a free XML sitemap generator. it's supposed to help peaple with their website indexing by making sitemaps super easy.

but i'm running into a really frustrating problem. sometimes, when users try to generate a sitemap for their site, it just throws up a 'file not found' error. it's not consistent, which makes it even harder to debug. it's like it can't access the target website's root sometimes, or maybe it's something with specific URL structures?

here's what the console output often looks like:

GET /generate?url=https://example.com/sitemap.xml 404 (Not Found)
Error: Could not retrieve resource at https://example.com/robots.txt
    at generateSitemap (sitemap-generator.js:123:19)
    at processRequest (server.js:45:7)

i'm totally stumped. is this a common issue with sitemap generators? like, server permissions, or maybe how i'm handling external requests? anyone faced this before?