Hello!
I have found that the feature "new" badge or tag was removed in the last versions of Open edX. See the commit: https://github.com/edx/edx-platform/commit/939a3672d4c2f65a6c8d04ebe7cacb621d8a1485
Why the new badge was removed? CSS styles are there because if you add the "<span class='status'> New </span>" it will appears the tag as in older versions.
Aspen version has the feature, but Dogwood not. You can check it out:
1. At Advance settings you can set a course as "is new" (aspen & dogwood contains this attribute)
Thank you.
Regards!