You get an error message like this one:
AJAX execution failed. Please first verify your module configuration. If the problem persists please send a screenshot of this page to the support.
Or :
Your are currently connected with the following domain name: (any domain) This one is different from the main shop domain name set in "Preferences > SEO & URLs":(configured domain)
Different possibilities, the most common is that the domain name you’re using does not match the domain name configured in your PrestaShop parameters, 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 that is configured, so as in this example;
http://www.mystore.com/admin
Other possibilities :
1 – You are hosted by a hosting company, for example OVH, with safety rules concerning the execution of Ajax script. Follow the recommendations of your provider about permissions on folders and files.
Troubleshooting guide for OVH: https://www.ovh.com/us/g1987.how_to_fix_the_500_internal_server_error
2 – Your store is in maintenance or your store front-office is not accessible, redirection or otherwise. It is not compatible with the functioning of the module, the module will only work if the store also works.