This issue is related to Moodle 4.0.
I haven't had the time to update the MoodleBox plugin in time, so this feature is missing as of now. I'm in the way to fix this. A workaround is to display the MoodleBox dashboard: buttons here works as expected. Sorry for the inconvenience.
Technical details: Moodle 4.0 changed the way the footer (and other visual elements) are displayed, so this needs a complete overhaul. I've yet to learn how to do this. Any help would be much appreciated.