Domain name with port rule for proxy

[xillibit]

Hello,

On my QNAP TS-673A, i have installed the following docker image jlesage/nginx-proxy-manager , in the NPM web interface under SSL Certificates, i have added my subdomain : cloud.domain.com.
On my registrar the pass.domain.com is linked to the IPWAN of my router which doesn’t change, on my router i have two ports redirected :
16895 => 192.168.0.227:443
16896 => 192.168.0.226:443
On my router the port 443 is already used by the user portal so i no others choices to use the ports 16895 and 16896
On NPM how to make the rule proxy to https://pass.domain.com: 16896 forwaded to 192.168.0.226:443 the rule that i have created :

On my QNAP TS-673A the network map is the following :

My rule doesn't work, when i open https://pass.domain.com:16896 i need to set an exception on firefox to open, it seems to doesn't pass by the NPM. How to solve that ?