I recently noticed a few isolated visits which are not tracked in Piwik 1.7.1 despite:
[li] The vast majority of visits are tracking fine.
[/li][li] There is no Do Not Track plugin or other privacy enabled.
[/li][li] The IP address is not blocked.
[/li][li] piwik.php is being successfully sent for each page with what looks like good data.
[/li][li] I resent the exact same query string using “curl” from one of my own machines and that did show up in the visitor log.
The only thing I can’t see/reproduce are the cookies. But I didn’t think there were any cookies whose presence or absence should cause an otherwise good piwik.php call to be ignored.
So what else could cause a visit to not show up in Piwik?