I'm finding that every time I turn on my PC, Defense+ is disabled. I've had it set on "Paranoid" and it's on when I shut down but disabled when I start back up.
To me it sounds like you have ticked Deactivate Defense+ permanently (Requires a system restart)
If this is correct please remove the tick, click OK and restart the system.
Found under Defense+, Defense+ Settings, General Settings (See Screenshot in red rectangle).