This problem occurs on PrestaShop versions prior to release 184.108.40.206. To fix this problem you will need to upgrade your store to the latest PrestaShop 1.6 version. Alternatively you can apply the fix manually as specified here.
- Where is the database connection file config/settings.php in PrestaShop 1.7
- How to setup cron job in cPanel to execute a URL
- How to get all customers who have never bought anything in PrestaShop
- How to get PrestaShop template page name with php
- How to get PrestaShop controller page name with php
- How to upgrade PrestaShop database only