You get an error message like this one:
The Ajax script execution failed. Please check your configuration and if the problem persists send a screenshot to Common-Services Support
Different possibilities, the most common is that the domain name you are using does not match the domain name configured in your Prestashop settings, your web browser sees a cross request between different domains which is a security issue prohibited by the browser itself.
Example, you log into your back office with the following URL:
http://mystore.com/admin
In your Prestashop configuration you have configured:
http://www.mystore.com/admin
Solution: You must use the same URL and log in to your store with the URL configured, therefore in this example;
http://www.mystore.com/admin
Other possibilities:
1 – You are hosted by a host, for example OVH, with safety rules concerning the implementation of Ajax scripts. Follow the recommendations of your provider about permissions on folders and files.
Troubleshooting guide for OVH: http://guides.ovh.com/InternalServerError
2 – Your store is in maintenance or the front office of your shop is not accessible, redirected or otherwise. It is not compatible with the functioning of the module, the module will only work if the store is also functioning.