Error at domaincheck validation nextcloud-aio


I’m struggling since a couple of days everytime blocking at the domain validation step, receiving that message error:

The domain is not reachable on Port 443 from within this container. Have you opened port 443/tcp in your router/firewall? If yes is the problem most likely that the router or firewall forbids local access to your domain. You can work around that by setting up a local DNS-server.

I’m on a brand new installation of Ubuntu 22.04, and using Nextcloud AIO docker, and for eventual external access, I have a free domain from no-ip. (

I got another installation to work about a couple of weeks, but that installation wizarded me to a free desec/dedyn domain name, but I don’t see that option to be available anymore. (Maybe, it was not the AIO docker but the VirtualBox vm)

Always restarting my installation of Nextcloud from scratch, I followed a lot of differents paths to try to make it to work.

  • I tried the main installation procedure
  • I used to follow the reverse-proxy thing by using the suggested along-side caddy docker. (I particularly “masterminded” a lot of adaptions always starting from the mains directives of the principal reverse-proxy path.)
  • I’m actually trying to use the local dns pihole docker suggestion with no more success.

Actually with that pihole setup, I see those ports open to listening:

CONTAINER ID   IMAGE                              COMMAND       CREATED             STATUS                       PORTS                                                                                                                               NAMES
e9e70b4b4611   nextcloud/aio-domaincheck:latest   "/"   32 minutes ago      Up 32 minutes (healthy)>443/tcp, :::443->443/tcp                                                                                               nextcloud-aio-domaincheck
35c5a25c4ce0   pihole/pihole:latest               "/s6-init"    About an hour ago   Up About an hour (healthy)>53/tcp,>53/udp, :::53->53/tcp, :::53->53/udp, 67/udp,>80/tcp, :::44080->80/tcp               pihole
4883634922e6   nextcloud/all-in-one:latest        "/"   2 hours ago         Up 2 hours (healthy)>80/tcp, :::80->80/tcp,>8080/tcp, :::8080->8080/tcp,>8443/tcp, :::8443->8443/tcp, 9000/tcp   nextcloud-aio-mastercontainer

I know that my port 443 is open in the aio-domaincheck docker:

netstat -tulpn | grep :443
tcp        0      0   *               LISTEN      973546/docker-proxy 
tcp6       0      0 :::443                  :::*                    LISTEN      973553/docker-proxy 

And for the validation that my pihole is correctly forwarding locally to my Ubuntu host lan interface (192.168.#.#, I can provide this:

PING (192.168.#.#) 56(84) bytes of data.
64 bytes from (192.168.#.#): icmp_seq=1 ttl=64 time=0.074 ms

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2053ms
rtt min/avg/max/mdev = 0.063/0.068/0.074/0.004 ms

Otherwise, outside of that pihole try setup, my ddns domain also seems to be pointing at my router wan ip, and a canyouseeme look on port 443 give me a success.

And from my router perspective, my port 443, 8443, 3478 (and 80 for sake of testing) are also forwarded to that Ubuntu host lan interface. (192.168.#.#)

I can provide other diagnosis informations if needed.

Do you have any idea of what’s going wrong here ?

À bientôt!