A:Answer Thank you for reaching out. All of the HDMI ports on your Pioneer 55" Class LED 4K UHD Smart Xumo TV are designed to support 4K resolution. However, to ensure your Xbox Series X is displaying in 4K, there are a few things to check. First, make sure the HDMI cable you're using is a high-speed HDMI cable, as older cables may not support 4K bandwidth. Second, navigate to your Xbox Series X's display settings and ensure that 4K resolution is enabled. Also, check your TV's picture settings to confirm that the HDMI input is set to "Enhanced" or "4K UHD Color" mode. Finally, try connecting the Xbox to a different HDMI port on the TV to rule out a potential port issue. If you've tried all of these steps and are still experiencing problems, please contact our Pioneer customer support team (1-800-421-1404) for further assistance. - Mae | Pioneer Support