An enhanced ecommerce action is needed to indicate attribution - list impression alone is not enough. On a subsequent interaction with that product, be sure to include the list in an actionField object (when it makes sense to do so in your purchase funnel). When you do this, also make sure that the id for the product is the same.
For example, on product click:
dataLayer.push({
'event': 'productClick',
'ecommerce': {
'click': {
'actionField': {'list': 'Dog Wet Food'},
'products': [{
'name': 'Royal Canin Yorkshire Terrier Adult Wet Dog Food',
'id': '100110',
...
}]
}
}
});
Note that if you send a different value for list on another enhanced ecommerce action involving this product, the attribution funnel may break. The list specified on the most recent action is the one that gets credit. So if you specified the list on a particular action, like product click, and you feel this is sufficient for attribution, then you don't need to specify the list on other actions like product add to cart. If you do need to specify the list on multiple actions, then make sure the value is the same, or if the value should be different on an action then just make sure that's what you really want to happen.