The requested content cannot be loaded. Unexpected response.

I get this message:
The requested content cannot be loaded.
Unexpected response.

I try to do it like this:

function show_make_offer() {
    $final_html = do_shortcode('[contact-form-7 id="7781180" title="Angebot"]');
    echo '
<h1>Sie haben noch Fragen zum Produkt?</h1>
Hinterlassen Sie uns eine Nachricht.
'.$final_html.'
';
}
 
add_action('woocommerce_before_single_product_summary', 'show_make_offer');

It works on an other website, but on my new test page it’s not working.
Form ID is right and everything looks good. If I Copy the Code like this in my page:

<h1>Sie haben noch Fragen zum Produkt?</h1>
Hinterlassen Sie uns eine Nachricht.
[contact-form-7 id="7781180" title="Angebot"]

it works. But I need to add this over the functions.php