In order to allow Remarkety to generate unique coupons and add them into your emails, you will need to verify your Webservice permissions.
1. From the PrestaShop menu, go to: Advanced Parameters -> Webservice -> Remarkety
2. Look for "cart_rules" row and make sure you check the following options:
View (GET), Modify (PUT), Add (POST), Delete (DELETE)
3. Click "Save" and you are all set.