We run the tests again by reinstalling it again.
It seems that the problem originated when we installed multiple Apps and then UptimeKuma somehow broke. So we installed them one by one, and now it's ok.
@girish Thank you. Your solution did the trick.
But we needed the ipv6 to be functional.
So what we did to make it work was > reinstall Ubuntu 22.04 LTS OS and didn't install unbound in advance. All is good now.