No hdr on YouTube app

@XfinityJodie​ yep,that’s the upgrade version of the Xi5.

Here are the detailed steps to Direct Message us:
• Click "Sign In" if necessary
• Click the "Direct Message" icon (upper right corner of this page)
• Click the "New message" (pencil and paper) icon
• Type "Xfinity Support" in the to line and select "Xfinity Support" from the drop-down list
• Type your message in the text area near the bottom of the window
• Press Enter to send your message

I'm not seeing anything known of that settings change. Let's take a closer look. Please send us a direct message with your full name and service address. 

Thank you for reaching out to us @bdriver! Do you currently have one of our 4K HDR devices? You can find the model number of your X1 TV Box by going to About in the X1 Settings menu. At this time, these are our compatible 4K rental devices:

• XG1v4 model numbers are AX014ANM or AX014ANC.
• XiOne model numbers are SCXI11BEI or SCXi11AIC or WNXI11AEI.
• Xi6 model numbers are AX061AEI or TX061AEI, listed as STB Version. 

Yes, it's the Xi6...TX061AEI. HDR/Dolby Vision works fine through other apps--and it used to work with YouTube app, as well. But then one day, YouTube HDR content won't render in HDR through this device. It works fine through the LG TV's native YouTube app.

I used to have an XG1v4 box, and the YouTube app never rendered HDR through that device, but the Xi6 did until just a couple of months ago. Bizarre.

Thank you for your feedback, @bdriver, and for sharing the equipment info. 4K YouTube content is available if you use the YouTube app on X1 and have an XG1v4 or Xi6 TV Box, or on Flex with a Xi6 or XiOne streaming TV Box, along with a compatible 4K or 4K/HDR TV. And so it seems like all the boxes are checked there. YouTube 4K badging is based on the highest resolution available of the video. YouTube 4K badging may display on an HD device, as the video will automatically downscale to the best-supported resolution and continue playback. Are you able to double-check the YouTube video's resolution within the YouTube app? And, are you launching the app using your Xfinity Voice remote? You can learn more including the FAQs about using the YouTube App on Xfinity X1 here.