Piwik for Magento only tracks one out of three shops



So I have setup a Magento Multi Store with three different shops and three different domains.
I created three seperate sites on the piwik website.
Now piwik only tracks one of the stores.
Iam using the piwik_ecommerce extension for Magento. I setup everything correct I think(since one store is working). The only difference between my three stores is, that they have a different Site-ID. I double checked the IDs for all three stores. What else could be the problem? Do I have to do any special configurations on the piwik-website?

Thank you for your replies