After upgrading to Joomla 3.6.5 (from, I forget which - should have made a note) the CiviDiscount navigation URL is broken (sends me to the CiviCRM dashboard). I also did a more minor update of CiviCRM to 4.7.14 (from 4.7.10ish) immediately after.
This question deals with a similar problem in Drupal. This is the URL that I am sent to from the menu: http://[site]/administrator/?option=com_civicrm&task=civicrm/cividiscount
What should it be instead?