Need help setting up local SSL certificates?

I followed this guide: https://notthebe.ee/blog/easy-ssl-in-homelab-dns01/

But my Nginx Proxy Manager is running on a VPS that is connected to my local network through a WireGuard tunnel. Could that be an issue? I don't know why it's not working?

My NPM is also accessible to the local IP of my homeserver on which WireGuard is running.