Also make sure you hit the select button when you choice "on", go back to the main menu and check the plug 7 icon.
If it has the U meaning something is conflicting
If it has a box simple, it's "Off"
If it has a black dot, it's "On"
Also when you put it on Manual, the icon should be "M"
If you try all of that and nothing work, let me know I will send you another DC8.