Also, I just checked, and my particular adblocker (uBlock Origin) has default rules that block Piwik too. Or, at least, anything installed in a /piwik/ folder. That particular rule comes from my subscription to the EasyPrivacy list, which is apparently available for
Adblock Plus too and is enabled by default on uBlock Origin.
Specifically, these are the rules:
/piwik-$domain=~github.com|~piwik.org
/piwik.$script,domain=~piwik.org
/piwik.php
/piwik/*$domain=~github.com|~piwik.org
/piwik1.
/piwik2.js
/piwik_
/piwikapi.js
/piwikC_
/piwikTracker.