Piwik has not been working for any of my sites lately. After thinking it over for a bit, it seems like it stopped working when I moved my Piwik setup and gave it its own subdomain. It used to be domain.com/piwik, with - obviously - the Piwik dir inside the web root of domain.com. Now it’s stats.domain.com with piwik in its own web root.
I don’t know what could be wrong. The tracking code appears correct, and everything seems to be working - except stats are not accruing at all.