According to posts made on the Apple Discussion Forums, iPhone and iPad users can no longer watch video from streaming platforms like Netflix, Amazon Prime Video, and HBO Max on a TV using an HDMI
Use your Apple TV remote to change video resolutions. For Apple TV 4K or Apple TV HD, hold Menu and Volume Down for 5 seconds. Apple TV will switch to a new resolution every 20 seconds. Select OK to choose a resolution or Cancel to quit. For Apple TV (2nd or 3rd generation), hold Menu and Up for 5 seconds.
Pretty sure at the moment it’s only Prime and Apple that have HDR10+ availability, other services are just Dolby Vision or HDR10. Netflix went with Dolby Vision. While HDR10+ and Dolby Vision are both backwards compatible with HDR10, they aren’t cross compatible with each other. What everyone else already said.
HBO Max may not work on your TV in USA due to outdated versions of your app and TV. Update your app and TV by following methods: HBO Max App: Highlight the HBO tile, press and hold the select button, select View Details and then Update. TV: Open settings, select System, and choose About > System update > Check for update.
sqpg.