Jetpack Contact Form — limitation
Jetpack 15.x requires a connection to WordPress.com before its contact-form module activates. Without that connection the [contact-form] shortcode does not register. To test, go to wp-admin → Jetpack → Connect, then re-add a Jetpack Contact Form block on this page.
Install Forms-by-Jetpack as a separate plugin if you do not want the full Jetpack stack.