for the results page:
the page created by the Data Assist wizard will contains a form tag around the repeat region.
before adding the eCart add to cart button to the results page, that form needs to be deleted.
once you delete the form around the results repeat region, you can replace the add to cart place holder with the eCart add to cart button.
see the "Integrating Data Bridge and eCart" tutorial on the Data Bridge support page for more details:
If you still need assistance, i'll need to see the problem online.