NGINX page won't load through HTTPS?

When I try to access NGINX Proxy Manager through Home Assistant “Open WebUI” it opens a page at https://duckdns:81 but it fails giving ERR_SSL_PROTOCOL_ERROR.

When I manually put in HTTP://IPADDRESS:81 I can access NGINX proxy manager so it IS running. What am I doing wrong?

My router is set up to use AdGuard Home as my DNS and forward port 443 to IPADDRESS. AdGuard Home redirects my duckdns to IPADDRESS in my network.

My external URL is https://duckdns
My internal URL is https://IPaddress:8123