If there are no lights at all, I would first check the power source and the fuse inside the charger if it has one. Did you try another outlet or cable to rule out a simple power issue?
For a passive solution, you might look at small SMD video isolation transformers rated for HD analog bandwidth and design a matched impedance network around them. Have you checked transformer specs for frequency response up to 4K CVI TVI ranges to ensure minimal attenuation?