Port 2015 is Caddy’s default port for serving sites. When Caddy manages TLS for you, it instead serves sites on ports 80 and 443 automatically. It’s not possible for Caddy to manage a third party certificate, so by providing one, you’ve disabled Automatic HTTPS.
My strong recommendation is to let Caddy manage your certificates instead of getting one from a website. As of a very recent update, Caddy can also provision wildcard certificates automatically. Automatic HTTPS — Caddy Documentation