SSH connection refused

[dropio]

Hello, I am really facing a riddle here and hope someone can help me solve it.

When trying to connect to the NAS via SSH, I get the message:
> ssh: connect to host nas.xyz.myfritz.net port 20000: Connection refused

The connection via HTTPS to nas.xyz.myfritz.net works and opens the TrueNAS UI. If I change the item Allow TCP Port Forwarding in the SSH settings (whether on or off), the connection is suddenly no longer refused and works. If I try the whole thing a day later, it starts all over again. First connection refused, setting changed, suddenly it works.

Platform: Generic
Version: TrueNAS-12.0-U8.1

Restarted the router and NAS several times with no luck and haven't come up with a better solution yet.

I would be very happy to receive any tips on how to solve this.

Edit, add additional information.
If any more information is needed, please let me know. I have little experience with TrueNAS and BSD in general.
- the NAS is a small box with an ASRock H110M-DVS R3.0 motherboard
- it is connected via ethernet to a Fritz.Box 7311 which connects to a DSL line
- my provider does not provide IPv4 anymore, but only a DS-Lite tunnel
- the Fritz.box does nothing more than share the NAS to both networks (no DMZ or something)
- the DynDNS service MyFritz from AVM is submitted to reach the box from outside
- port shares are set up for https (443) and SSH

 

[Glorious1]

That is quite a riddle. I wonder if you solved it?

 

[dropio]

Thanks for your reply, I do not have a solution to this problem yet.

 

[ChrisRJ]

You did not provide a lot of information. E.g. the hostname seems to indicate that you want to access from outside your local network. If so, that is critical information for us. So please try to provide as much detail as possible, and also think about what information would/could be relevant for someone who does not know anything about your setup.

 

[dropio]

Thanks for your answer. I have extended my first post to this effect.