WordPress – Detect successful response from ajax function

I have a function which is triggered via AJAX and will run the following when successful:

wp_send_json_success();

I am then doing a console log of the response and trying to detect if success = true:

.done(function (response) {

if( response['success'] == true ) {

    console.log('add to cart successful');

} else {
    
    console.log('add to cart failed');

}

Currently I am getting "add to cart failed" despite the output of response looking like it should be successful:

console.log(response);

// Response in the browser console:

{"success":true}

Am I detecting the true response incorrectly?

Update – PHP function the AJAX is triggering. Removed most code just as a test.

function fbpixel_add_to_cart_event_conversion_api() {

    echo 'hello world';

    wp_send_json_success();

    die();

}
add_action('wp_ajax_fbpixel_add_to_cart_event_conversion_api', __NAMESPACE__.'\fbpixel_add_to_cart_event_conversion_api');
add_action('wp_ajax_nopriv_fbpixel_add_to_cart_event_conversion_api', __NAMESPACE__.'\fbpixel_add_to_cart_event_conversion_api');

$.ajax({
    url: MyAjax.ajaxurl,
    type: 'POST',
    dataType: 'json',
    data: {
        action: 'fbpixel_add_to_cart_event_conversion_api',
        product_id: productId,
        variation_id: variationId,
    },
    })
    .done(function (response) {

    console.log(response);
    console.log(productId);
    console.log(variationId);
    console.log(response.success);

    if( response.success === true ) {