Urgent: Dynamic XML Sitemap for Laravel SEO Failing with Cache Clear Errors

I'm completely stuck and desperate for help. We're experiencing critical issues with our 'Dynamic XML Sitemap for Laravel & All Websites' package; every cache clear breaks our Laravel SEO sitemap generation, making it inaccessible or throwing 500 errors. I've been troubleshooting for hours, and here's a consistent error from the logs:

[2023-10-27 14:35:01] local.ERROR: file_put_contents(/var/www/html/public/sitemap.xml): Failed to open stream: Permission denied {"exception":"[object] (ErrorException(code: 0): file_put_contents(/var/www/html/public/sitemap.xml): Failed to open stream: Permission denied at /var/www/html/vendor/sitemap-package/src/SitemapGenerator.php:87)

Any immediate solutions or debugging advice would be a lifesaver. Please help!