It could be the cable what resolution are you trying to send?
Bridging the gap between audio and video in one dynamic cable, you can connect your Blu-ray player, computer, AV receiver, Apple TV, Roku, cable box, Play Station 3, Play Station, Xbox One, 360, Nintendo Wii, Wii U or other HDMI compatible devices to your Ultra 4K TV (UHD TV), HDTV, monitor, or projector. The AmazonBasics HDMI cable displays 4K video at 24 Hz, 1080p at 60 Hz, with 48-bit deep color, and supports bandwidth of 10.2 Gbps
As per the above description the cable is only rated for 4K @ 24Hz. You need a cable rated at 18 Gbps something like the below:
I could be that the Xbox is outputting at a lower bandwidth.
There is an option to output at 4:2:2 in the system settings also an option to limit the colour depth to 8-bit. You could try both these settings to see if they work on your N2 since this could be display related.
Have you tried those setting without the soundbar (N2 directly connected to the tv)?
The most important thing is setup your tv properly to show HDR from that HDMI input where the N2 connected. Also use a fresh install without any add-on.
I would still look around the tv settings.
I tried CE on Samsung, Philips and LG tvs without any HDR problem.
N2 is my daily driver and HDR works great with my LG tv.
Do you have a chance to try your N2 on another tv?