Sorry, I have read many suggestions about configuring ports in this forum but none have solved my problem.
Tixati works fine - much better than Transmission which I used before.
If I stop DHT then re-start it, it goes through "Connexion" to "Online". But after a few minutes it says it is online but the port is blocked. It lists 329 nodes (this number varies).
My system:  Windows 11, Ethernet with a 4G modem/router. No ISP account (uses SFR). Mullvad VPN.
I specifically authorised Tixati in the firewall (Windows Defender) and opened the TCP and UDP ports, in and out (for good mesure):
4001, 6881-6889, 6969. Tixati says it is using 22208 so I added that too.
The modem shows UPnP for Tixati ext. 22208 - int. 22208 for TCP and UDP  (set by itself).
What else do I need to do to unblock this port?  Which port?
(Does it really matter that DHT says the port is blocked? - it has a lot of nodes and everything works fine.)

What you are facing is not a blocked port but a bug, as far as I have experienced. Use a port mapper app to forward that port(22208) and then start Tixati. Tixati has a somewhat broken port forward that works if you have a public IP, but doesn't work in a shared IP or vpn. I am facing the same problem, and you can take a look at my post: https://forum.tixati.com/support/8710

I have solved the issue using a portmapper, but a Fix from the Tixati side would help very much. Help us KH.

Thanks.
Even though DHT claims the port is blocked, it has a list of nodes which changes constantly: from less than 300 to over 400 and back down again.
And in the graph of processed transactions there is plenty of "find nodes" activity shown.
So it seems to communicate anyway.
In the log it shows many events for IPv6 - but this is simply not activated at all in my system. Could this be the real problem?

this problem still exists and now does not connect to other clearnet peers.
I have tried both qbittorrent and biglybt and they become fine after a few minutes but only tixati shows online port blocked.

I downgraded my client to v3.41 . No more DHT error / bug .

how did you downgrade to 3.41? i cant find it?

here is a link to downgrade.
https://tixati.com/download/tixati-3.41-1.win64-install

does not work.
it says online when you click on dht tab,  but when you go deeper into node table > ipv4. THen status is shown as - online port blcoked 29 buckets 443 nodes.

So, Sad.