How to open a port on a Zyxel Keenetic II router?

Question

MTS

This question is for owners of a device from a subject or its analogues with the same control interface. Perhaps someone has already encountered such a problem and can tell.
First, introductory:
The router is connected to the network via an MTS connection modem, IP is dynamic, therefore dynamic DNS is configured and working.
The problem is that I can’t set up a web face for the Transmission client built into the router, the gui client on android constantly displays a Connection timeout or Connection refused message. After much tinkering, it turned out that the reason for this could be a closed port, which is not visible from the outside. I checked the ports with different services, including on the manufacturer's website: zyxel.ru/openport
Two questions:
1. If the port is closed in the router, how to open it correctly?
2. Can the port be closed on the ISP side?
I would be grateful for help.

Answer 1

I thought that everyone already knows that 34G modems are behind the NAT provider.