I see. Since the review average displays, then you did activate it for that post type – so here could be other causes for it not to show up:
- Are you using
<?php comment_form(); ?>
to display your comment form?
- If so, make sure
do_action( 'comment_form_logged_in_after');
and
do_action( 'comment_form_after_fields');
are present and not modified by other plugins or functions, by:
- Deactivate Other Plugins to see if that fixes it.
- Switch theme to make sure the Theme is not affecting it. E.g. In the Twenty-thirteen Theme by WP, they are present by default when using
<?php comment_form(); ?>
to display for comment form.
On a side note: What version of WP are you using?
The review field should display if no other plugin or function is affecting the comment form, so do try that and let me know?