AJAX request from Chrome Extension to Wordpress Website

I developed a chrome extension which extract some data from the user visiting page and I want to transmit them to my database by an AJAX call (my website is a basic wordpress website).

The point is that the ajax response is error 400 and I do not understand where is the problem as I tried to modify my ajax request the best I could.

Here is my AJAX request from content.js

/* Popup clicked */

$('#myOwnCustomToolBar_TT91 #message_to_click form.groupio_form #subscribe').on('click', function(){

    chrome.runtime.sendMessage(product_infos);


});

Here is the new background.js file :

chrome.runtime.onMessage.addListener(function(response, sender, sendResponse){

        jQuery.ajax({

        type:"POST",
        url: "https://www.groupio.fr/wp-admin/admin-ajax.php",
        contentType: 'json',
        dataType: "JSON",
        responseType:'json',

        data: {
            action : "itempricingfunction",
            ean : "EANTEST0101010"
        },

        success:function(data){

            alert(data);

        },

        error: function(errorThrown){
            console.log(errorThrown);
        }
        });

});

Here is my function called itempricingfunction inside the functions.php file of my wordpress theme file

function itempricingfunction(){


$product_ean = (isset($_POST['ean'])) ? htmlentities($_POST['ean']) : NULL;
echo json_encode(array('product_ean' =$product_ean));


    exit;
}

add_action("wp_ajax_nopriv_itempricingfunction", "itempricingfunction");
add_action("wp_ajax_itempricingfunction", "itempricingfunction");

And finally, when I go to the product page and click on the chrome extension, the response of the ajax call is Error 400.

Thank you very much for your help !