To be able to help, we will need a little ore information.
Here are a few things to check:
After adding the new columns to the eCart object, did you upload the WA_eCart folder to the server?
Did you create the cart display page before or after adding the new columns?
If you created the cart display page before adding the new columns, they will not be included in the display manager. You may want to try recreating the cart display, when adding the Display manager to the page, make sure to select the new columns to the display on the second step of the wizard.
If you still have problems, please compress a copy of the page with the add to cart button on it in a zip file and attach it to your reply. It would also be helpful if you provided a link to your site.