It sounds like your "last visit" date is not updating when you log out. Check it and see (hover the mouse over your username on the menu bar). It happens to me a lot.
Thanks Graham4405 - I did just that and reset the time to January 30 at 19:30, then logged out, then deleted browsing history and cookies, closed the browser and rebooted the PC.
All now is up to date - too well so in fact as looking for the new posts resulted in the following - which I guess translates to "NONE".https://www.railpage.com.au/f-s-id-newposts.htm
Could not obtain topic idsDEBUG MODE
SELECT p.topic_id FROM nuke_bbposts p, nuke_bbforums f WHERE p.post_id IN () AND f.forum_id = p.forum_id AND f.forum_id NOT IN (31, 35, 37, 41, 45, 46, 47, 48, 49, 50, 51, 52, 54, 56, 64, 65, 67, 68, 71) GROUP BY p.topic_id
Line : 528
File : /srv/Railpage.com.au/www/public_html/modules/Forums/search.php "
I will see how it goes after the next few days - and yes, it doesn't seem to be updating when one departs - it is about one visit behind.
Edit - yes, the error message does seem to be the response when there are no new posts - after posting the above I had another look, and just one shows - this one.