Up unto last week my Drupal site and varnish_purge worked together fine with Varnish. After updating the modules to the latest versions, cache tag invalidation seemed to stop. Nothing else really changed in the meantime. In /var/log/varnish/varnishncsa.log I get messages like the following.
127.0.0.1 - - [16/Nov/2021:09:04:13 +0100] "BAN http://127.0.0.1:6081/ HTTP/1.1" 200 254 "-" "varnish_purger module for Drupal 8."
In the syslog there are no messages from Varnish or Drupal.
After changing something on a page,
drush p:queue-work should give a notice like the following.
Processed 5 objects...
It instead shows the following.
The queue is empty or has only locked items!
How should I debug this?