You have to pull fuses in your towed 12V Kit attach to battery vehicle to be able to tow it. This usually knocks out power to your stock 12-Volt outlet.
Disconnect Battery for Towing
Many towed vehicles now, have to have the towed battery disconnected for towing. This is very common in Ford and GM vehicles, though not exclusive.
Bad 12-Volt Outlet
Some towed vehicles simply have a 12-volt outlet that doesn't work. When that is the case the 12-Volt Battery Direct Kit is a great fix.