Unable to fetch article bodies from specific group

[Ben Finney]

Howdy all,

I'm trying to use Gnus with my ISP's Usenet service,
‘news.internode.on.net’. (That will refuse access from anyone not using
Internode as an ISP.)

When I visit a group such as ‘news.groups.questions’, this works fine: I
can fetch the article headers and bodies. However there is a specific
failure:

When I use Gnus with ‘news.internode.on.net’ to read ‘comp.lang.python’,
I can fetch the summary (which I presume fetches the header of each
article), but attempting to fetch *any* article body, old or new, gives
the message “No such article (may have expired or been canceled)” from
Gnus.

When I use ‘telnet news.internode.on.net nntp’ and speak the NNTP
protocol, I *can* fetch any article body from that group with the ‘BODY’
command.

What could be causing this? How can I diagnose it further, or fix it?

-- 
 \        “If you have the facts on your side, pound the facts. If you |
  `\     have the law on your side, pound the law. If you have neither |
_o__)                       on your side, pound the table.” —anonymous |
Ben Finney