I’ve also found that for a shortcode-only field, you should make sure “Formatting” for the field is set to “Convert HTML into tags” and not “No formatting”.
I had a text field set to:
[contact-form-7 id=”3650″ title=”My Contact Form”]
and when using:
echo do_shortcode(get_field('myfield'));
it would display as:
[contact-form-7 404 “Not Found”]
It was only when I changed “Formatting” to “Convert HTML into tags” that the shortcode was expanded properly.
