Make sure the HDMI cable you are using is HDMI 2.2 compliant.
Make sure if your are using a 4K TV you go into the TV options and set the TV setting to accept 4K pass through from the Player to the TV
Make sure your TV supports more than 1 HDMI input that is 2.2 compliant. If only 1 input is compliant you will need to switch your cable to that input.
Make sure you are using a USA region Bluray Disc. Not all Blu-ray disc are Region Free meaning if you bought something on the internet and had it shipped from overseas... possible you are using a Region Locked Bluray disc.