A:Answer Call Hisense customer service. I had a similar situation occur for my Apple TV 4k. Everyone, including Hisense told me ports 3 + 4. I tried high speed cables, and the works. NOthing worked. i even called Apple and complained. Called Hisense, gave them my serial number (Important) and the guy told me that they switched it to ports 1 + 2. He was able to look this up by my serial number. I was doubtful, but tried it. Boom! 4k HDR automatically switched.
The rep was happy for me and said that serial numbers for this model, made AFTER a certain date (Forgive me, but I forgot), 4K is HDMI ports 1 +2.
Hope this helps! Wish I would have known.