404: An error occured

ENOENT: no such file or directory, stat '/nix/store/4rmrfnbq4b1k9yq6scx6wac6dl0l7cyy-pixie-pages-v0.0.6/libexec/pixie-pages/deps/pixie-pages/web/sitemap.xml'

You can use the Site Tester to check for any configuration errors.