Datepicker not working

Contact Form 7 has some Datepicker support via the new HTML5 date input type (see https://contactform7.com/date-field/) but this is currently only supported on some browsers – see https://www.wufoo.com/html5/types/4-date.html

Contact Form 7 does provide jQuery UI-based fallback for the date and number input fields. See https://contactform7.com/faq/does-contact-form-7-support-html5-input-types/

You can now also use Contact Form 7 Controls to implement this without writing any code – use the “Enable HTML5 input type fallback” option.