Check in ~/.tin for files that might have set the server incorrectly.
printenv NNTPSERVER and make sure it's correct. Check that
/etc/nntpserver is readable and correct. After those are set,
in your current shell, try again. Edit ~/.tin/newsrctable and ~/.newsauth. Note usenet in 2025 almost always requires signup and (free) servers are hard to find. Tin is pretty hardcore. I used to use it years ago, but if you can't get it working, just as a test try Emacs (Gnus), Pan, or Slrn. When you know your connection is fine then you can debug the Tin issue. You might try the "-D " flag with appropriate debug item.
Following this guide worked with my news server substituted in for the example one:
https://news.individual.net/configur...9-linux-en.php except for the password (utf-8 errors?). I use Gnus though and it works with Gnus so this doesn't bother me.