This is the default fallback page served by Caddy when no site matches your request. It usually means the server is freshly installed, or your DNS is pointing here but no Caddyfile entry covers the requested hostname.
A record (or AAAA) at your DNS provider that points to this host.dig +short yourdomain.tld to check./etc/caddy/Caddyfile with the same hostname.sudo systemctl reload caddy.Caddy will request a certificate from a public CA on the first request and renew it automatically while the service runs.
Reference manual at caddyserver.com/docs. Community forum at caddy.community.