On this page:
http://developer.piwik.org/api-reference/tracking-api
It says this:
idgoal — If specified, the tracking request will trigger a conversion for the goal of the website being tracked with this ID.
And it later says this:
you must set &idgoal=0 in the request to track an ecommerce interaction: cart update or an ecommerce order.
To work around this, we’re posting the ecommerce transaction twice - once with idgoal = 0, which causes it to recognize the ecommerce order, and once with idgoal =the id of the goal, which causes Piwik to recognize a transaction.
Piwik is supposed to create the conversion based on a URL match, but it doesn’t.
Hi Richard
Please create bug report if you can reproduce a particular issue