Why Your Nginx SSL Certificate Shows as Self-Signed (When OpenVPN Is Installed)

Symptom: You have a valid Let’s Encrypt certificate installed on your Nginx/Virtualmin server, but browsers show a self-signed certificate warning instead. The Nginx configuration looks correct, and openssl s_client from the server itself returns the right certificate — but external connections return the wrong one.

If OpenVPN Access Server was installed on your server before Nginx/Virtualmin, this article is for you.