Error Message

Usually the key is generated automatically. However, if your wp admin email is invalid, this will fail. You can manually generate the key here: https://pdf.ninja/

Once you generate a key, you have to import it on your site.

The key is located on Contact Form 7 ‘Integrations’ page (https://yourdomain.com/wp-admin/admin.php?page=wpcf7-integration). Click the edit button and you will be directed to this url: https://yourdomain.com/wp-admin/admin.php?page=wpcf7-integration&service=pdf_ninja&action=edit

Once there, you can paste the key and save. This should fix your issue. Let me know if this doesn’t work.