If you haven't yet, also try restarting the ATV. If this doesn't work, it still might be the cable. Apple says use a cable certified for DV, but, I think you can find one with the HDMI certification on it. Not all cables will have enough bandwidth for the added HDR metadata, if the cable is HDMI 1.4, but, not made to spec, it could create a bottleneck. This may not be the issue, but, first thing I would try. https://www.hdmi.org/manufacturer/premiumcable/faq.aspxI’m not seeing DV anything as an option in ATVs menu. 4K HDR 30hz and 24hz, yes. Both of which I tried but still only getting HDR.