You have a new 4k TV. Make sure you are using HDMI 2.1 cables (new 2019 standard), and not HDMI 1.4 cables (old 2009 standard). A 1.4 HDMI will not give you reliable 4k video because it transfers video much slower than a newer 2.1 version of HDMI. If you are not sure which cable you have, just buy a new 2.1 and enjoy! I understand why people may thing there's no difference because they look exactly the same, But there is a HUGE different is you have an older cable, which most were if you go back 2 years.
Your reply is not totally accurate. The HDMI 1.4 cable transfers 4k at 30fps so it will work. the newer hdmi spec'd cable will provide for up to 8k resolution, but the contour boxes, unless you are using one you got 5 years ago, are coming with the latest spec hdmi cable. I still have one from a contour box I upgraded to in 2020 when i was still working for Cox, and the one I received had a 2.1 version hdmi cable with it.
best answer, if you got your contour box within the last few years, you have the right cable and don't need to go buy one.