Reinstated on each page the piwik code to track site stats
Joomla you must go to the administration panel> Extensions> Manage Plug-ins> Folcomedia - Piwik, then complete the following two fields (see image 1)
"URL of your piwik" (internet way to access your piwik - see image 2)
"Id piwik for your site" (Site ID in piwik - see image 3)
If you made a copy paste of your field "URL of your piwik" you should get this page.
So on the "Id piwik for your site" it is found at Settings> Sites