So there should be no SSL until you hit your NGINX Proxy Manager instance. If you can't get HTTPS to work make sure your firewall is appropriately port forwarding to your NGINX Proxy Manager SSL port.
The forwards should look something like this if you are using the Proxy Manager App in Unraid:
Firewall -> Internal Port
80 -> <ip of unraid host>:1880
443 -> <ip of unraid host>:18443