Dynamic text field not populating

Hi there,

I have followed this tutorial (https://sevenspark.com/code/how-to-create-a-dynamic-wordpress-contact-form) with the aim of populating a form field with the post title of the post the user was previously on.

In my post template file, I have added the code:

global $post;
echo '<a href="https://www.neuautolease.com/ldnal15sb/?page_id=66?car='.urlencode(get_the_title($post->ID)) .'">Get A Quote</a>';
?>

In the form I have set up a dynamic text field which produced this short code:

[dynamictext dynamictext-33 uneditable “CF7_GET key=’car'”]

When the link is clicked, the post title is added to the url of the form like this:

https://www.neuautolease.com/ldnal15sb/?page_id=66?car=Audi+TT+Roadster

But the dynamic text field is not being populated.

Have I missed something out or made a mistake?
Any help would be hugely appreciated!

https://www.ads-software.com/plugins/contact-form-7-dynamic-text-extension/